65
HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING USED BY A GROUP OF FORM FIVE STUDENTS by Liu Hui Kuen A THESIS SUBMITTED TO THE SCHOOL OF EDUCATION OF THE CHINESE UNIVERSITY OF HONG KONG IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS IN EDUCATION July 1982

HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

  • Upload
    others

  • View
    1

  • Download
    0

Embed Size (px)

Citation preview

Page 1: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING

USED BY A GROUP OF FORM FIVE STUDENTS

by

Liu Hui Kuen

A THESIS

SUBMITTED TO THE SCHOOL OF EDUCATION OF

THE CHINESE UNIVERSITY OF HONG KONG

IN PARTIAL FULFILMENT OF THE REQUIREMENTS

FOR THE DEGREE OF

MASTER OF ARTS IN EDUCATION

July 1982

Page 2: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions
Page 3: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

2

ACKNOWLEDGEMENTS

S.C.Chong, my supervisor, for hisI wish to thank Dr.

supervision and assistance at every stage of the study.

I thank Mr. David Lau for helping with the assessment of

intercoder agreement, Mr. C. M. Chung for his valuable suggestions,

and Miss Eileen Tso for refining the language.

Finally, I thank my family for their encouragement and

support in my study.

Page 4: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

3

HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEM-SOLVING

USED BY A GROUP OF FORM FIVE STUDENTS

ABSTRACT

This is an exploratory study of the heuristic strategies

used by a selected group of Form Five students in solving

to-prove problems in plane geometry. Subjects were individually

interviewed in the problem-solving test, and were instructed to

verbalize their thought throughout the problem-solving process.

Their protocols were tape-recorded, and coded according to a

coding system modified from Kilpatrick's system. To check

reliability co-coding method was used.

It was found that, of the 22 heuristic strategies

identified, 16 could be reliably coded. The result of factor

analysis on the problem-solving variables showed four factors

underlying geometrical problem-solving performance. The dominant

factor is logical ability, which accounted for 40% of the variance.

The other factors are use of strategJ, use of goal-orionted

syntheses and mathematics attainment. Altogether the four factors

accounted for 87% of the variance.

The result of this study showed that logical ability is

the basic ability involved,'that mathematics attainment only plays

a minor role, and that mastery of the problem-solving techniques

is essential to success in geometrical problem-solving.

Page 5: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

TABLE OF CONTENTS

ACKNOWLEDGEMENTS ii

ABSTRACT iii

LIST OF TABLES vi

Chapter

l. INTRODUCTION 1

2. REVIEW OF RELATED LITERATURE 4

2.1 Literature related to task variables 5

2.2 Literature related to subject variables 6

2.3 Literature related to process variables 8

2.4 Literature related to instructional variable 10

2.5 Techniques for studying problem-solving processes 12

3.BACKGROUND OF THE STUDY 15

4.STATEMENT OF THE PROBLEM 17

5. THE RESEARCH DESIGN 18

5.1Subjects 20

5.2 Pilot test 20

5.3 The coding system 21

5.4 Assumptions 27

5.5 Data analysis 27

5.6 Limitations of the study 28

Page 6: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

296• FINDINGS

357. DISCUSSION AND CONCLUSION

398. RECOMMENDATIONS

398.1 Suggestions for further research

408.2 Irplioatious in education

APPENDICES

42A. Problem_solving test paper

43B. Set of problem-solving variables

44C. Coding' form for problem-solving protocols

45D. A sample of two written and coded protocols

48E. Marking scheme

51F. Glossary

53BIBLIOGRAPHY

Page 7: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

6

LIST OF TABLES

Table

3110 List of variables reliably coded

2 . Varimax rotated factor analysis on the

32problem - solving variables .

Page 8: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

1

Chapter 1

INTRODUCTION

Three aspects of teaching mathematics in school are

computational proficiency, concept attainment, and problem-

solving (LeBlanc, 1977). Some mathematics educators even state

that the ultimate goal of school mathematics is problem-solving

(Lester, 1977). The call for problem-solving techniques to be

formally taught in classrooms is gaining increasing support.

Research.-in problem-solving is still in the exploratory

stage (Kelm and Bussmann, 1980), and systematic investigation

of the topic is rendered very difficult by its complex nature

(Lester, 1980). Although psychology and mathematics education

have shared common interest in problem-solving, there is little

agreement of viewpoints, and it has remained, for over 30 years,

the most chaotic field in human learning. One reason for this is

that a variety of tasks have been used in research. The tasks

ranged from simple manipulations in elementary arithmetic to

complicated puzzle problems such as the Tower of Hanoi. Another

reason is that researchers held very different positions on the

nature of problem-solving. Behaviorists, gestaltists, and proponents

of information processing have different interpretations on the

same problem-solving behavior.

Page 9: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

2

A typical study of problem-solving in the sixties and

the earlier Period was to make deductions on the problem-solving

performance of subjects from their personal characteristics. Such

characteristics included Intelligence Quotient, spatial ability,

various language abilties, socio-economic status, mathematics

ability, and many others. Though these studies did give valuable

information about the problem-solving process, they only served

to provide guidelines for theory building. They were criticised

for over-emphasizing the product aspect, being interested only in

the number of correct solutions and in the time for solution. They

had neglected the more important aspect-- the process. How one

thinks during problem-solving is fundamental.

In order to obtain a clear picture of the problem--solving

situation some researchers began to conduct clinical studies on a

relatively small number of subjects. These studies generated

exciting hypotheses, but subsequent verification was handicapped

by the lack of a commonly accepted instrumentation scheme.

In the past decade, mathematics education researchers

devoted more attention to problem-solving than to any other topic

in the mathematics curriculum (Lester, 1980). Although psychologists

have run slightly ahead in establishing a theory of problem-solving,

mathematics educators realize that mathematical problem-solving

heeds a unique theory, rather than a generalization or specialization

of the psychological one. As a result of strenuous efforts devoted

Page 10: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

3

to such research, knowledge about mathematical problem-solving is

accumulating rapidly, but a skeleton for the systematic theory has

not yet been built up (Kulm and Busamann, 1980).

Researchers have learned that the key to the study of

problem-solving is to understand the mental operations behind.

Mental operators are of two types: algorithms and heuristics. An

algorithm is a set of rules, which, if followed, will generate

the correct solution. Rules of multiplication and solving a

quadratic equation by formula are examples of algorithmic. Heuristics

are procedures or outlines guiding the search for solutions. Rather

than an exhaustive trying out of all appropriate algorithms, a

heuristic is a method of tentative search. The use of heuristics

is often based on the effectiveness in solving previous problems.

Unlike algorithms, heuristic methods do not guarantee success.

Human thinking is particularly skilled in the use of heuristic

methods. A good chess player solves his problem heuristically he

could not possibly see the consequences of every move. In fact,

most interesting and complicated problems are seldom solved by

algorithms. In some cases, appropriate algorithms may not even

exist.

Page 11: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

4

Chapter 2

REVIEW OF RELATED LITERATURERELATED

Research in mathematicalproblem - solving relevant to this

study can generally be classified into four categories , corresponding

to four types of variables associatedwith the topic .

( a ) Task variables- - factors associatedwith the nature

of the problem.

( b ) Subject variables- - - characteristicsof the individuals.

( c ) Process variables- - factors related to problem - solving

behaviors.

( d ) Instructionalvariables- - features of the problem - solving

environmentexternal to the problem and the problem - solver .

These variables interact with each other to a very large

extent making mathematicalproblem - solving look so subtle and

complex as to defy , descriptionand analysis . After reviewingthe

studies in connectionto the above variables , the techniquesfor

studying the problem - solving processeswill be examined .

Page 12: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

5

2.1 Literature related to task variables

The results of previous mathematical problem-solving

research could not be easily generalized because a wide diversity

of problems had been used. The problems included direct computatio:

in the elementary school mathematics curriculum (Robinson, 1973),

word problems in arithmetic and algebra (Caldwell, 1978 Sanders,

19?3Kilpatrick,1967), calculus (Lucas, 1974), geometry (Caroll,

1977), cryptarithmetic problems (Newell and Simon, 1972), series

and matrices (Babad and Bashi, 1978), and puzzle problems such as

the Tower of Hanoi.

In a study to examine the interaction between problem

structure (simple versus complex) and cognitive level (concrete

versus formal) of eighth grade students, Days, Wheatley and

Kulm (1979) concluded that problem structure played a greater role

in determining process use for. formal than for concrete students.

They also found evidence that problem structure had a greater

effect on problem difficulty in the forma,. group than in the

concrete group.

Webb (1975) conducted a study with algebra students and

found that the processes used by students depended in part on

problem characteristics such as structure and content.

Bans and Nelson (1978) investigated the effects of

distractors in different settings on problem-solving performance

Page 13: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

6

of grades 1-3 schoolchildren. They found that irrelevant information

affects problem-solving ability, but the effect decreases with

increasing age. Of all distracters, spatial-numerical ones were

the most troublesome. Caldwell (1977) studied the effect of

extraneous data included in a problem on the problem-solving

performance of school geometry students. He found that there was

a reduction in achievement when extraneous data were included, but

the effect was the greatest with those students using an analytic

strategy. He also found that the position of the extraneous data

was influential.

2.2 Literature related to subject variables

Scandura (1977) pointed out that individual differences

measurement is a relatively neglected aspect of human problem--solving.

Despite this, individual differences such as sex, cognitive ability,

mathematical aptitude, attitude towards mathematics, and the

relationship of these differences to problem-solving ability have

been investigated by a number of researchers.

Some researchers conducted studies to investigate sex

differences in problem-solving ability. Fennema (1974) and

Fennema and Sherman (1978) found that males are not superior to

females in mathematical problem-solving. However, Wilson (1972)

found evidence that males perform much better than females.

Page 14: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

7

Meyer (1978) studied the structure of intellectual

abilities related to mathematical problem-solving. By administering

a battery of 20 tests of various abilities and employing a factor-

analytic technique, she was able to conclude that intellectual

structures contained a specific mathematics ability. In addition,

Verbal, Reasoning (Induction), Numerical and Perceptual Speed

abilities were present in the intellectual structures.

Suydam and Weaver (1977) found evidence that IQ was not

significantly related to problem-solving ability, that sex difference

did not exist in problem-solving ability, and that socio-economic

status alone did not appear to be a significant factor,

In his classic twelve-year study of mathematics abilities,

Krutetsltii (1976) attempted to identify the characteristics of

successful mathematical problem-solvers, and found four different

types of abilities that poor problem-solvers lacked. He further

classified students into three types according to their mathematical

cast of mind: analytic, geometric.and ha.r.Tonic. In addition, he

found no evidence to support the belief that males are superior to

females in mathematical problem-solving.

Silver (1979) found that good problem-solvers are superior

to poor problem-solvers in their ability to perceive the mathematical

structure of a problem and to generalize the method to problems of

similar structures.

Page 15: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

8

Robinson (1973) investigated the problem-solving behaviors

and the cognitive and affective characteristics of sixth grade

children, and found that good problem-solvers had significantly

higher scores in IQ, reading comprehension and self-esteem, and

lower scores in test anxiety.

2.3 Literature related to mess variables

Kilpatrick (1967) investigated the problem-solving

behaviors of eighth grade schoolchildren as they solved mathematical

word problems. To analyse their protocols he devised a coding

system based on the heuristic processes identified by Polya (1957).

Among the processes and heuristics Kilpatrick observed in his study

were drawing a figure, using successive approximation, questioning

the existence and the uniqueness of a solution, using deduction,

using an equation, using trial and error, and chocking the solution.

Of all the heuristics he studied, only using successive approximation

had a significant correlation with the tot'll score.

Webb (1979) studied the relative importance of conceptual

knowledge and process use in mathematical problem-solving. He

identified three heuristic components, namely, mathematical

achievement, pictorial representation, and verbal reasoning.

Pictorial representation was interpreted to represent the processes

related to drawing or using figures. He also found that conceptual

knowledge and process use are intercorrelated. Since conceptual

Page 16: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

9

knowledge does not appear to be the unique heuristic component, he

concluded that the use of some processes is important in solving

problems beyond existing conceptual knowledge.

Kantowski (1977) conducted a clinical, longitudinal study

of problem-solving on a group of 8 algebra students. By employing

this paradigm she was able to observe in depth the problem-solving

behaviors of these children. Her study revealed that successful

problem-solving is associated with the consistent use of heuristics

in general and goal-oriented heuristics in particular, and with the

regular use of analyses and syntheses as a pattern. She found that

failure to introduce a heuristic often led to superfluous analyses,

while on the other hand the suggestion of a heuristic not related

to the goal resulted in superfluous syntheses. She also found that

the use of looking-back strategy was not related to success in

problem-solving.

Caroll (19?7) investigated the relative effectiveness of

three strategies, namely, analysis,' syntheis, and combination in

problem--solving. She found that analytic strategy was related to

less stable achievement levels than synthetic or combination

strategies. The proof construction skills of students using

analytic strategy were not as consistent as the skills displayed

by students using the other two strategies. She considered analysis

not the optimum strategy for students.

Page 17: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

10

In Hong Kong, Lee (1981) identified a problem-solving

model in physics and mathematics consisting of the following five

stages: perceiving, subgoal formulating, rule-searching, rule-

applying, and verification. He found that success in the whole

problem-solving process depends on the problem-solver's ability

to perform each stage. Further, he found evidence that problem-

solving ability is not significantly related to sex and to IQ.

2.4 Literature related to instructional variables

Polya (1957) dealt extensively with instructional techniques

in heuristic methods. Problem-solving, he claimed, is a practical

skill. Like other practical skills, it can be acquired through

imitation and practice. He urged teachers to solve problems before

the class to demonstrate how problem-solving can be achieved. The

teacher should verbalize his thought, he should drammatize his

ideas a little, and he should put to himself the same questions

which he uses when helping his students.

LeBlanc .(1977) identified two kinds of strategies in

mathematical problem-solving: general and helping strategies. A

general strategy may be thought of as an overall plan to solve the

problem. A helping strategy may be thought of as an intermediate

step to carry out the general strategy. Some general strategies

are trial and error, organized listing, simplication, searching

for a pattern, deduction, computation and working backwards. Some

Page 18: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

11

helping strategies are diagram, tables, graphs, lists and equations.

Both of these strategies can be and should be formally taught in

the classroom.

Post and Brennan (1976) investigated the effects of various

modes of presentation of general heuristic processes on students'

problem-solving ability. They found that formal instruction in a

heuristic model suggesting general components of the problem-solving

process is not effective in promoting problem-solving ability.

Lucas (197k) investigated heuristic usage and problem-solving

performance, and-analyzed-the effects of heuristic-oriented

teaching on a group of first year university calculus students. He

found significant differences all favouring the instructional

treatment on the following heuristic strategies: using mnemonic

notations, using method/result of related problem, separating and

summarizing data. Further, he found evidence that students receiving

instruction in heuristic processes exhibited superior overall

performance in approaching problems, devising workable plans, and

obtaining accurate results.

Vos (1976) examined the effects of three instructional

strategies on the following heuristics: drawing a figure,

approximating and verifying, constructing an algebraic equation,

classifying data, and constructing a chart. He found that the

group of subjects without instructional treatment were less likely

to exhibit the effective use of the five heuristics. In addition,

Page 19: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

12

he found evidence that mathematical maturity was a definite factor

in mathematical problem-solving.

2.5 Techniques for studying problem-solving processes

The product's variables of a problem -solving situation can

be quantitatively measured to high precisions Such variables include

the solution time and the score in the test. However, these

variables do not adequately reflect the whole problem-solving

situation, which is internal within the subject neither do they

permit inferences about the particular path an individual takes in

reaching a solution. To study the problem-solving processes, a

number of different ways have been devised and used to get subjects

to generate observable sequences of behavior.

(a) Introspection

Subjects have to observe and reports on their mental processes

as they solve a problem. This method is time-consuming and requires

careful training and practice under controlled conditions. But

psychologists believe that thinking may be distorted by requiring

the subject to observe himself thinking as he solves the problem.

(b)' Retrospection

This method does not require the subject to observe his

Page 20: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

13

thought as he works. Instead he is asked to recall his thought

processes after he has completed a given task. The interviewer

will often ask questions about his particular path of thought.

However, it is difficult for the subject to remember all the steps

in his thought processes, including errors and blind alleys, and

in reproducing these steps without rearranging them into a more

coherent, logical order (Kilpatrick, 1967).

(c) Thinking-aloud

This technique requires the subject to think aloud as he

works. It permits lengthy observations and the use of subjects

without training. They do not have to think and observe themselves

at the same time. One possible disadvantage of this technique is

that thinking may inhibit speech. Thinking may be so rapid that

it may not be followed or precisely stated by speech, and subjects

may remain silent just when his thought is the most active. However,

Roth (1966) found no significant differences in the number of

correct solutions, the solution time, and the mode of imagery

between subjects required to think aloud while solving reasoning

problems and subjects not required to think aloud. Hafner (1957)

gave an individual performance teat to two matched groups of

children, with one group instructed to vocalize what they were

thinking and doing as they worked. The vocalization group took

slightly less time and obtained slightly more correct solutions

than the non-vocalization group, but both differences were not

statistically significant.

Page 21: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

14

(d) Problem-solvinginventories

Written inventories attempt to incorporate aspects of one

technique or a combination of the above techniques into a written

form, to save the trouble of audiotaping and protocol coding. Further,

with written instruments data can be obtained from a relatively

large number of subjects in a relatively short period of time.

However, these inventories have the disadvantage of restraining

the subjects' responses, since they present to the subject a list

of alternatives rather than requiring him to generate his Own. No

structured-choice test can be expected to give an adequate picture

of the problem-solving processes.

Over the past two decades, most research in mathematics

education employed the thinking-aloud technique (Dana and Nelson,

1978 Days, Wheatley and Kulm, 1979 Kantowski, 1977 Webb, 1975

Wheatley, 1980). Others used problem-solving inventories (Babad

and Bashi, 1978 Caroll, 1977 Fennema and Sherman, 1978 Meyer,

1978). The thinking-aloud technique' is use• in exploratory studies

to generate future hypotheses, while the problem-solving inventories

are used to validate such hypotheses'.

Page 22: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

15

Chapter 3

BACKGROUND OF THE STUDY

Although a great deal of research has been devoted to

mathematical problem-solving, the goal of establishing a

comprehensive theory is still far from sight. Even less has been

revealed in geometrical problem-solving. Few studies have been

conducted in the area consequently, investigation in this field

is still at the preliminary stage.

Under such circumstances one intending to study geometrical

problem-solving may hypothesize any regular patterns he observes

concerning the problem-solving variables and then test his

hypotheses. In order to obtain a valid conclusion, he must draw

a representative sample from the population for his test. Due to the

heavy work load imposed by the large number of subjects involved,

he must rely on problem-solving inventories-- paper and pencil

tests. But, as pointed out earlierv these 41nventories restrain

the subjects' responses, and are not suitable for use in exploratory

studies.

However, the writer is more inclined to study in greater

depth the process aspect, and not the product aspect as emphasized

in the inventories method. In this case he must draw a sample,

generally not representative, in order to study the problem-solving

variables in detail. Any conclusion generated from this study, then,

Page 23: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

16

will suffer limited generalizability because of the size of the

sample.

This study is exploratory rather than experimental, and

observations will be made on a small group of subjects. Neither

a control nor comparison group will be used. The writer will not

pose any well-defined hypotheses beforehand, since the aim is not

to test and validate such hypotheses. Rather, the purpose is to

search for regularities which will serve as a basis for plausible

hypotheses for future studies.

Page 24: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

17

Chapter 4

STATEMENT OF THE PROBLEM

This study aims at finding answers to the following

questions:

What are the main heuristic strategies the selected(a)

group of Form Five students use when they solve plane geometry

to-prove problems?

(b) Among the problem-solving variables, can a structure

of geometrical problem-solving performance be determined?

Page 25: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

18

Chapter 5

THE'RESEARCH DESIGN

This is an exploratory study to investigate the heuristic

strategies used by Form Five students in solving geometry to-prove

problems. The relation between these strategies and other

problem-solving variables will also be examined,

Subjects are to solve three geometry to-prove problems.

The first two problems are solvable by two or more methods, each

method involving constructing an auxilliary line followed by an

application of appropriate theorems in certain areas of the

geometry curriculum. The areas involved are congruent triangles,

parallelism, and other topics such as tangent and chord properties.

The third question consists of three parts. Each part is actually

a hint for the solution of the following part, and the whole

question aims partly at testing the student's ability to understand

the hint as implied in the question. The question resembles real

questions in open examinations. A copy of the three problems is

given in Appendix A.

In this study, the principal technique is the thinking-

aloud method. Subjects are instructed to verbalize their thought

as they solve the problems, and the interviews are tape-recorded.

Whenever a subject falls silent for a minute or more, the interviewer

Page 26: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

19

will ask non - leading questionssuch as " What are you thinking

now ? " , " Please tell me everythingyou are thinkingabout . " etc .

For those subjects who cannot fluently verbalize their

thought , the retrospectiontechnique will be used to supplement

the thinking - aloud method . The interviewer will intermittently

interruptthe subject ' s thought , if he remains silent for a

long time , and ask what he is thinkingabout . At the end the

interviewerwill ask questions on the path the subject takes

in reaching the solution .

All the interviewswill be tape - recorded. During the

interview the interviewer observes the subject solving the problem

and takes down important notes related to the variables as listed

in the coding form . The data for process - sequenceand checklist

variablescan be found from the tape - recordedprotocols, and the

solution time from . the tape readings . The protocolsare coded

accordingto the coding system as explainedin Section 5 . 3 ,

referencebeing made to the interviewer' s notes and the subjects '

The answer scripts will be marked according to the marking

scheme given in Appendix E . Further the mathematicsresults of

the subjects throughoutthe year will be recorded from the

School file , and these are taken as the mathematicsattainments

of the subjects . All these variablesare subject to data analysis .

scratchwork.

Page 27: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

20

5. 1 Subjects

The subjects in this study are a group of 40 male studei, t+

chosen at random from three Form Five classes in the school where

the writer teaches.

5. 2 Pilot test

The writer chose three geometry to- prove problems as

test questions and designed a set of 36 problem- solving variables.

A pilot test was conducted in April 1981 to five students in the

manner described above. However, the result of the test indicated

that the problems were, on the average, rather difficult for the

students, and not raquoh useful information could be obtained from

their protocols. The writer decided to give up using these problems

and chose a new net of three geometry to- prove problems. A copy of

the new set is given in Appendix A.

The second pilot test was conducted in December 1981

during Christmas' holidays. The test was administered to eight

students. The now set of problems seemed ideal for use in this

study. The pilot test was used to refine the set of problem- solving

variables. As a result, 11 variables were dropped, and 25 variables

were retained for analysis. The final set of problem- solving

variables is given in Appendix B.

Page 28: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

21

5.3 The Coding System

The coding system employed in this study is a codification

of Kilpatrick's (1967) and Lucas' (1972). The Kilpatrick system

was based on the heuristic processes identified by Polya (1957),

but it also included categories for various non-heuristic

processes, types of errors, and incidental comments, The coding

system had two parts: a process--sequence code and a checklist.

The process-sequence code was used to translate the

subjects' behaviors into a string of symbols that characterized

their attempts to understand the problem, to produce a solution,

and to check the solution. A glance at the string of symbols

would adequately reflect the whole problem-solving situation.

The checklist dealt with supplementary, non-sequential

information in greater detail. Items on the list were checked

when the corresponding behavior first occurred. Subsequent

occurrences during the solving of,the same problem were not

recorded.

The Kilpatrick system had 52 behavior variables of which

27 were checklist variables, 5 process-sequence codes, and the

rest performance measures.

The coding system adopted in this study is the outcome

Page 29: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

22

of the second pilot test conducted earlier. The present system had

15 process-sequence variables, 7 checklist variables, and 3

performance measures.

The process-sequence variables are represented by symbols,

and their meanings are given in the list below.

Process Symbols

R= Reading an trying to understand the problem

C= Constructing auxilliary elements

S= Applying a theorem to given or derived condition and working

forwards

A= Applying a theorem to the conclusion or derived conclusion

and working backwards

H= Using algebraic processes such as setting up an equation,

substituting, manipulating, etc.

The quality of the outcome of the processes Construction,

Working Forwards and Working Backwards (C, S, and A) is rated and

is represented-by a number from 1 to 3, where

1= incorrect-

2= correct, but inappropriate or superfluous

3= correct, and goal-oriented

For example, if a student constructs an auxilliary line that is

not helpful to the solution of the problem, this is coded as C2.

Page 30: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

23

Checklist Variables

Mnemonic Notation

This item is checked if a student uses mnemonic notations

such as marking a right angle with two perpendicular line strokes,

or drawing a circle through three non- collinear points. Occurrence

of this behavior is easily observed from what the student has

written on the figure.

Using all given conditions

This is coded if the student has used all conditions given

in the question, irrespective of whether he can arrive at the

result or not.

Devisinga plan before writing doh

This is coded if a student can show that he has devised

a plan before writing down in the answer sheet. Occurrence of this

behavior can be observed during the interview.

Ap roachin the problem in terms of con runt triangles

This is coded if a student proves Question 1 or Question 2

using properties of congruent triangles. Both questions require the

student to prove two line segments equal. Occurrence of this

behavior is observed from the student' s verbal protocol and his

written work.

Page 31: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

24

Approaching the problem in terms of parallelism

This is coded if a student attempts Question 1 or Question 2

using properties of parallel lines. This can also be observed

easily from the student's verbal protocol and his written work.

A roachin the problem in terms of other alternatives

This is coded if a student approaches a question in terms

of theorems other than congruence and parallelism, such as chord

properties, Pythagoras theorem, etc.

Understanding the hint as implied in the question

This is coded if a student in doing Question 3 can use the

result of part (a) to prove part (b), or can use the result of (b)

to prove (c).

Performance Measures

The solution time

This is the time the student requires for solving the

problem, and can be obtained from the tape readings.

The Score of the Test

The writer marks the answer script to give this score. The

papers are marked according to a fixed scheme as given in Appendix E.

Page 32: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

25

Mathematics attainment

This is measuredby the student ' s examinationresults in

mathematicsthroughout the year ,

A copy of the coding form is given in AppendixC . The coding

form has three parts . The first part is a space for writing

process - sequence symbols . Comas are used to separate successive

processes. A virgule ( / ) indicatesthat the student stopped work

without obtaining a solution , and a full stop indicates that the

work was completedwith a solution .

From the process - sequence code the coder can determine

which of the three proof - constructionstrategies the student has

adopted : synthesis , analysis or combination.

Proof - construction strategies

Synthesis

The student using this strategy begins with the hypotheses

or conditions and yields deductionsuntil the conclusion is reached .

His process - sequencecode will thereforecontain only S ' s and

noA .

Page 33: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

26

Analysis

The student using this strategy begins with the conclusion

and reasons that it must be the conclusion of some propositions

Through analytic reasoning, a chain back to the hypotheses is

formed. His process-sequence code will therefore contain only

A's and no S.

Combination

The student employing this strategy works both forwards

from the hypotheses and backwards from the conclusion until the

two chains of reasoning are connected. His process-sequence code

will therefore contain at least one A and one S.

After coding the process-sequence variables, the coder

counts and writes down the frequency of the occurrences of each of

the processes. From this he can determine the proof-construction

strategy and checks in the appropriate space. The three proof-

construction strategies are included in the process-sequence

category.

From the process-sequence code, the coder can also find

out the number of theorems a student quoted during problem-solving,

which is the algebraic sum of all S's and A'a. The number of

theorems quoted is abbreviated n in the coding form and is included

in the process-sequence category.

Page 34: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

27

The second part of the coding form is for checking the

checklist variables, and the third part for entering the performance

measures.

As an illustration of how the coding system operates, two

verbal protocols were transcribed and given in Appendix D. The

protocols were coded according to the coding system, and the codes

were shown following the written protocols.

5.4 Assumtions

In this study the following assumptions will be made:

(a) Vocalization of thought does not affect the problem-

solving process to a deleterious extent (Roth, 1966 Hafner, 1957).

(b) Subjects in this study will try their best to vocalize

their thought, since participation in the test is strictly optional.

5.5 Data analysis

The coding system gives rise to 15 process-sequence

variables and 7 checklist variables. The protocols of ten subjects

will be coded by another coder B. Scott's formula will be used to

Page 35: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

28

calculate the coefficient of agreement between the coders for each

variable. Variables with low inter-coder agreement( T 0,83)

will be dropped.

Varimax rotated factor analysis will be applied to the

remaining variables to study the structure of geometrical

problem-solving performance.

5.6 Limitations of the stuff

This study suffers the following limitations:

(a) The sample is too small to permit generalization to

any population.

(b) The thinking-aloud technique demands a great deal of

manpower for interviewing the subjects and analyzing their protocols.

The present scope of the study is just wit*n the writer's ability.

(c) The thinking-aloud method might be unreliable since an

individual might remain silent during moments of deepest thought.

The retrospection method might not be able to supplement this

weakness adequately.

Page 36: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

29

Chapter 6

FINDINGS

The proper problem-solving test was conducted to the

selected group of 40 students during Easter holidays in April

1982. One student did not turn up for the test another said that

he was unwilling to participate. One participating student could

not verbalize his thought at all. Another student said that

verbalization of thought seriously distracted his attention and

distorted his thinking. The last two students were below-average

students in the non-science stream.

Therefore four more students were invited to participate

to make up to the number of forty. The test was conducted in the

same manner as the pilot test. From the tape-recorded protocols,

the interviewer's notes, the rough work and the written solutions,

the writer coded verbal behaviors'of the subjects. The solution

time was read from the tape readings, and the answer scripts

were marked to give the scores of the test. From the school file

the yearly mathematics result was taken, giving the mathematics

attainment for each student.

The writer coded all protocols. Then protocols of 10

students were coded by another coder B. Coder B is an experienced

Page 37: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

30

mathematics teacher. The data obtained for each variable by the

two coders were compared for agreement using Scott's formula.

As a result of applying Scott's method for the reliability

check of the coding procedure, one checklist and five process-

sequence variables were dropped for low inter-coder agreement

( C 0.83). The checklist variable dropped is mnemonic

notation, and the five process-sequence variables dropped are

construction (wrong), construction (superfluous), working forwards

(wrong), working backwards (wrong), and analytic proof.

The remaining variables are listed in Table 1 on the

next page. Their abbreviations are also given. The variables

are arranged in descending order of frequency of occurrence, with

the first variable occurring most frequently, and the last

variable occurring least frequently.

Page 38: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

31

Table 1

List of Variables reliably coded

AbbreviationsVariables

theorems1. Number of theorems quoted

goal-or synthesesWorking forwards (goal--oriented)2.

alg processUsing algebraic processes3.

all conditionsUsing all conditions`t.

read5. Reading question

synthetic prf6. Synthetic proof

sup synthesesWorking forwards (superfluous)7.

plan8. Devising a plan

goal-or constConstruction (goal-oriented)9.

other approachApproach: others10.

understand hintUnderstanding the hint implied11.

congr trianglesApproach: congruence12.

goal-or analysWorking backwards (goal-oriented)13.

combination pry'14. Combination proof

parallelism15. Approach:. parallelism

sup analysesWorking backwards (superfluous)16.

Page 39: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

32

Table 2

Varimax rotated Factor Analysis on the Problem-solving Variables

Factor kFactor 2 Factor 3Factor 1

MathematicsUse ofUse ofLogicalAttainmentStrategyAbility goal-oriented

Syntheses

0.92goal-or analyses

-0.97synthetic prf

0.97combination prf

0.65alg process

0.84theorems

0.82sup syntheses

-0.72plan

0.69solution time

o.61goal-or synthese8

o.8kall conditions

0.570.63test score

0.65attainment

10.213.522.9kO.2% variance

86.963.1T O. 2 76.6Cum% variance

Page 40: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

33

The 16 variables that could be reliably coded, together

with three performance measures, namely, mathematics attainment,

test score, and aolution time, were submitted to data analysis. The

result of applying varimax rotated factor analysis to the 19

variables is given in Table 2 on page 32. Factor loadings greater

than 0.5 are given. The name given to each factor is also included.

The result of factor analysis on the data shows that

geometrical problem-solving is dependent on four factors or

abilities. The first factor includes three problem-solving variables,

namely, the use of synthetic and combination (of synthetic and

analytic) proof strategies, and the analysis of the to-prove

conditions in a direction towards the given conditions. These

variables are at a more advanced level than the others. They are

related to the logical ability of the problem-solver. Hence this

factor is called logical ability. The fact that it accounts for

40% of the variance shows that logical ability dominates geometrical

problem-solving performance.

Factor 2 was concerned with the use of strategy. It included

using algebraic-processes (setting up equations, substitution,

manipulation, etc.-), applying theorems, synthesizing heuristically

the given and obtained conditions, devising a plan, and time.

These are strategies demanded in most problem-solving situations,

and are not specific to geometrical problem-solving. It should be

noted that devising a plan would help to narrow the scope of the

Page 41: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

34

search for solution and hence to save much effort and time. This

general factor accounted for 22.9% of the variance. Concerned

with the general use of heuristic strategies in most problem-

solving situations, this factor was named the use of strategy.

Factor 3 was readily identified as the use of goal-oriented

syntheses. It included three variables, namely, working forwards

(goal-oriented), using all conditions, and test score. Given a

whole set of seemingly unrelated conditions, the problem-solver

might start his heuristic search by synthesizing the given conditions

in all combinations and in all directions. The successful problem-

solver would be-more likely to discriminate the goal-oriented

syntheses from the superfluous ones than the poor problem-solvers.

Repeated use of goal-oriented syntheses on all given conditions

would probably lead to solution and hence higher scores in all

tests. Again, this factor is not specific to geometrical problem-

solving. It accounted for 13.5% of the variance.

Factor 4 consisted of two4variab] s-- mathematics

attainment and test score. This factor is named mathematics

attainment. It accounted for only 10.2% of the variance. This

shows that attainment played only a minor role in geometrical

problem-solving. It can be inferred that geometrical problem-solving

might be quite different from mathematical problem-solving.

Page 42: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

35

Chapter 7

DISCUSSION AND CONCLUSION

The conclusions in this study may apply to the selected

group of students only, which may also serve as a basis for

plausible hypotheses for future research in a larger scale.

The four factors identified-- logical ability, use of

strategy, use of goal-oriented syntheses, and mathematics

attainment- accounted for 86.9% of the total variance. Factor

loadings of the'variables were high. The factor-analytic technique

has helped to reveal the structure of the geometrical problem-

solving process. The performance can be explained by four factors,

corresponding to four types of abilities. The dominant factor

is logical ability. This ability is involved in the goal-oriented

analysis of the to-prove condition, and the construction of an

appropriate overall proof-construction strategy. The breaking

down of the to-prove condition helps to reduce the complexity

and abstractness of the problem. The proof-construction strategy

signifies an overall systematic attack on the problem. Due to its

structure and settings, a geometry to-prove problem demands more

logical ability of the problem-solver than other mathematical

problems at the secondary level. Therefore this ability is specific

Page 43: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

36

to geometrical problem-solving in the mathematics curriculum at

the secondary level.

The other three factors are quite general to mathematical

problem-solving. The use of strategy includes a batch of general

problem-solving techniques: using algebraic methods, applying

rules (theorems in geometry), searching heuristically by synthesizing

given and obtained conditions, and devising a plan. Iheee techniques

can be acquired through instruction and experience. The effective

use of goal-oriented syntheses depends to a large extent on the

problem-solver's ability to distinguish the important elements

from the distracting and superfluous ones. This ability may not

be easily acquired through instruction, at least through a short

interval of time. Finally, mathematics attainment appears as the

least important factor. These three factors altogether accounted

for 46.7% of the total variance.

The result of this study gives partial support to

Kantowski's finding (197k) that supcess iA,solving geometry and

verbal problems was associated with the use of goal-oriented

heuristics. The-factor, use of strategy, identified in this study

confirmed Polya's (195?) second step of problem-solving. The

existence of the attainment factor is consistent with the findings

of recent research concerning mathematical problem-solving

(Meyer, 19?8 Webb, 1979).

Page 44: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

37

The answers to the research questions posed at the outset

are given below. They. are plausible answers subject to the

limitations of this study.

(a) What are the main heuristic strategies the troup of Form

Five students use when they solve plane eometr to-prove problems?

The main heuristic strategies reliably coded are listed

below. They are arranged in descending order of frequency of

occurrence, with the first item occurring most frequently and the

last item occurring least frequently.

1. Number, of theorems quoted

Working forwards (goal-oriented)2.

3. Using algebraic processes

Using all conditions4.

5. Reading question

6. Synthetic proof

Working forwards (superfluous)7.

8. Devising a plan

Construction (goal-oriented)9.

Approach: others10.

Understanding the hint implied11.

Approach: congruence12.

Working backwards (goal-oriented)13.

14. Combination proof

15. Approach: parallelism

Working backwards (superfluous)16.

Page 45: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

38

(b) Among the probsolvin ariables y can a structure

of geometrical roblem,-solvin erformance be determined?

The main factors underlying geometrical problem-solving

performance, in decreasing order of significance, are: logical

ability (40.2%), use of strategy (22.9%), use of goal-oriented

syntheses (13.5%), and mathematics attainment (10.2%). The

figure within parentheses indicates percentage of variance

accounted for by each factor. Altogether these four factors

accounted for 86.9% of the variance.

Page 46: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

39

Chapter 8

RECOMMENDATIONS

8.1 Suggections for Future Research

The result of this study depends to a certain extent on

the choice of test questions. So, as a follow-up, this study can

be complemented using other geometry questions of different

styles and of different degrees of difficulty. Further, the same

research can be conducted on girls to study if there exists any

significant difference in the sexes in geometrical problem-solving.

In all these cases the same coding system and research design

can be used as in this study.

Similar studies can be conducted using geometry to-find

problems in the problem-solving test. However, the coding system

has to be modified because more algebra and arithmetic are involved.

In view of the fact that the thinking-aloud technique

necessitates time-consuming and tedious protocol analysis, which

might be subjective and unreliable, some objective means of detecting

processes should be considered. After such an objective means is

devised, the problem-solving studies can be conducted in larger

scale and scope in order that more valid and generalizable

Page 47: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

40

conclusions can be drawn. But objective problem-solving inventories

tend to inhibit the problem-solver's responses, as pointed out

earlier. More research should be done in the area of instrumentation.

8.2 Implications in Education

This study shows that logical ability is vital for

proficiency in geometry. Plane geometry, for thousands of years,

has been studied, and helps the learner to build up a logical cast

of mind. In addition, plane geometry is still very useful in

several branches of science and technology. Though Euclid's geometry

has been criticised, its position in the secondary school

curriculum cannot be paralleled by statistics and probability.

Geometry is the essential, logical part of the school curriculum:

sets and logic may be too difficult for the average student. In

Hong Kong, much of the geometry content has been sacrificed for the

introduction of such topics as statistics, probability, and

coordinate geometry. The training8of students in the logical aspect

is reduced. Curriculum designers are urged to bear this in mind

and to review the present situation.

The use of strategy is important to geometrical problem-

solving. Teachers are urged to teach these problem-solving

strategies to the students. They should frequently demonstrate

how they solve a problem by drammatising their thinking processes

a little to help students learn the techniques of problem-solving.

Page 48: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

41

They should show students how they distinguish the goal-oriented

syntheses and analyses from the superfluous ones. The suggestions

in Polya (1957) are valuable.

In Hong Kong, few mathematics textbook writers have made

any contribution to the techniques of problem-solving. The

approach in worked examples in geometry is exclusively synthetic

in nature. They never show how they analyse the to-prove condition

in a meaningful way. They only show what result is achieved: they

never mention how the result is achieved. To stimulate the learner's

interest and to promote his problem-solving ability, textbook

writers should pay more attention to the process aspect of problem-

solving.

Page 49: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

42

PROBLEM-SOLVING TESTAPPENDIX A

Do ALL questions. A rough work sheet and an answer sheet are provided.

Write down your answers in the answer sheet.

Figure 1DO ALL OF YOUR THINKING ALOUD

D

C1. In Figure 1, AOB is a diameter

0of the circle, centre 0. A smaller circle BA

is drawn with diameter A0. A chord AD of

the larger circle cuts the smaller at C.

prove that AC= CD.

Figure 2D Y

2. In Figure 2, a circle is drawn

C

with diameter on side AB of ABDT

cutting BD at C. The tangent XCY cuts

AXAD at T. If CT is perpendicular to AD,

prove that AD= AB.

Figure

A3. In Figure 3, ABC is an

equilateral triangle inscribed in a

Dcircle. P is any point on minor arc BC.

D is a point on AP such that PD= PB.

Prove that (a) BDP is equilateral

CB(b) ABD BCP

(c) PA= PB+ PC

P

Page 50: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

43

SET OF PROBLEM-SOLVING VARIABLESAPPENDIX B

Process-secguence variables

R= Reading and trying to understand the problem

M= Using algebraic processes

C= Constructing auxilliary elements (wrong/superfluous/goal oriented)

S= Applying a theorem to given or derived condition and working

forwards (wrong/superfluous/goal-oriented)

A= Applying a theorem to the conclusion or derived conclusion

and working backwards (wrong/superfluous/goal-oriented)

n= Number of theorems quoted

Synthetic proof.

Analytic proof

Combination proof

Checklist variables

Mnemonic notation

Using all given conditions

Devising a plan before writing down

Approaching the problem in terms of congruent triangles

Approaching the problem in terms of parallelism

Approaching the problem in terms of other alternatives

Understanding the hint as implied in the question

Performance measures

Mathematics attainment

Solution time

Test score

Page 51: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

44

APPENDIX C CODING FORM FOR PROBLEM-SOLVING PROTOCOLS

Tape readingsCoderSubject no.

Solution timeDateProblem no.

PROCESS-SEQUENCE

AlSlClRfrequency count:

A2S2C2M

A3S3C3n

proof-construction strategy

combinationanalysissynthesis

CHECKLIST

Mnemonic notation

Using all given conditions

Devising a plan before writing down

Approaching the problem in terms o P congruent triangles

Approaching the problem in terms of parallelism

Approaching the problem in terms of other alternatives

Understanding the hint as implied in the question

PERFORMANCE MEASURES

ScoreSolution timeMathematics attainment

Page 52: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

45

A SAMPLE OF 2 WRITTEN AND CODED PROTOCOLSAPPENDIX D

Process-

sequence CodeStudent No.8Question 1

RReads problem

SlAC x AD= AO x ABD

AO 是 diameterC

AO: OB

AO B

AC x AD= 两 个 AO

ACx AD=2AO2

Reads problem again

CD= AD- CA

所 以 AC x AD= AC x 2AC

= 2 AC2

M

R

AC= AO

AC= CDM

Student No. 1Question 2

RReads problem

D 即 是 要 證 這 两 個

相 等 。 要 證 這 兩 個Y

T

XA B

A3

Join CA C3

S3

C 加 這 個 =90°

但d 加 這 個 (?)=90°

因 為 , 所 以 t=d

S3

S3

M

angle(t,d)

angle,

Page 53: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

46

APPENDIX 6 CODING FORM FOR PROELEM-SOLVING PROTOGOLS

Subjoct no 8Coder A Tape readings

problem no 1 Date Solution time

PROCESS-SEQUENCE R, S1, M, R, M

frequency countR 2

M 2

N 1

C1

C2

C3

S1 1

S2

S3

A1

A2

A3

proof-construction strategy

synthasis amalysiscombination

CHECKLIST

Haomoaio notation

Using all given conditions

Devieing a plan before writing down

Approaching the problem in iorms of congruent triangies

Approaching the problem in terms of parallelism

Approaching the problem in terms of other alternatives

Understanding the hint as implied in the question

PERFORMAECE MEASURES

Mathemation attainmont Solation timeScore

Page 54: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

47

APPENDIX C CODING FORM FOR PROBLEM-SOLVING PROTOCOLS

Subjoct no

Problem no

Coder

Date

Tape readings

Solution time

PROCESS-SEQUENCE R,A3,C3,S3,S3,S3,M

frequency countR

M

n

C1

C2

C3

S1

S2

S3

A1

A2

A3

proof-construction stratagy

synthesis analysis combination

CHECKLIST

Maemonic notation

Using all given conditiens

Davising a plan before writing down

Approaching the problem in terms of congruent wriangles

Approaching the problem in terms of parallelism

Approaching the problem in terms of other Alternatives

Underatanding the hint as implied in the question

PERFORMANCE MEASURES

Mathemation attainment Solution time Socre

Page 55: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

48

MARKING SCHEMEAPPENDIX E

MarksSolution steps1.

Join OCD

2ACO= 900

C0 is the centre

2AC= CD0BA

Quoting reason:

1from centre to chord

total 5

MarksSolution step1. (alternative method)

Join OC, ODD

2ACO= 90C

2Proving ACO=DCO

1AC= CDA

0

total 5

MarksSolution stems1. (alternative method)

Join OC, DBD

2ACO= 90°

C1Proving CO // DB

AO= OBA B0

2AC= CD

total 5

Page 56: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

49

MarksSolution steps2.

Join CAD

Y 2B

2DProvingC

B= LD

AB= AD 2Ax B

6total

MarksSolution steps2.(alternative method)

Join ACD

Y 2C4

2C3ProvingCC3 C4

1ACD = ACBProvingT

B 1AD= ABA

x6total

MarksSolution steps2. (alternative method)

Join CO

OCY= 90 0D 2Y

1OC// AD

CDB

T

2or OB/OA= OC/AD

BA0X 1AD= AB

6total

Page 57: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

50

Solution steps Marks

0

1

2

3

1

1

1

3

1

1

1

3

DBP is equilateral

(a)total

BD = BP

Proving

Proving BCP BAD

(b) total

AD = PC

AP = AD + DP

= PC + PB

total

3.

A

BC

D

P

Page 58: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

51

GLOSSARYAPPENDIX F

Heuristic

(a) As a noun, it means the study of the methods and

rules of discovery and invention. Descartes, Leibnitz and Bolzano

were pioneers in heuristic.

(b) As a noun it means a heuristic method or strategy.

Hence the terms heuristic, heuristic method and heuristic strategy

are synonyms.

(c) As an adjective, it means serving to discover.

Problem

A problem is a situation in which an individual or group

is called upon to perform a task for which there is no readily

accessible algorithm which determines completely the method of

solution. This definition is due to Lester (1980).

Problem-solving

Problem-solving is the set .of acti-ons taken to perform

the problem task.

Problem-solving variables

These are variables that are related to, or will exert

influence on, the whole problem-solving process. In this study,

the variables include 15 process variables (R, M, n, C1, C2, C3,

Si, S2, S3, Al, A2, A3, synthetic proof, analytic proof, and

Page 59: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

52

combination proof),7 checklist variables (as listed in the

coding form), 3 performance measures (mathematics attainment,

solution time and test score), making up a total of 25.

Geometry to- rove problem

Geometry problems are of two types: to-find problems and

to-prove problems (Polya, 1957). In to-find problems we are given

the data, the condition and the unknown. In to-prove problems

we are given the hypotheses and the conclusion. To-prove problems

are considered to be at a more advanced level than to-find

problems, because they demand more deductive ability than the

latter.

Page 60: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

53

BIBLIOGRAPHY

Babad, E.Y. and Bashi, J. On narrowing the performance gap in

mathematical thinking between advantaged and disadvantaged

children. Journal for Research in Mathematics Education,

1978, 9(5), 323-348.

Banal, J. and Nelson, D. Distractors in non-verbal mathematical

problems. Journal for Research in Mathematics Education,

1978, 9(1), 55-61.

Barnett, J.C. Toward a theory of sequencing: Study 3-7: An

investigation of the relationships of structural variables,

instruction and difficulty in verbal, arithmetic problem-

solving. Dissertation Abstracts International, 1975, 36(1),

99A.

Caldwell, J.H. Cognitive development and difficulty in solving

word problems in mathematics. Dissertation Abstracts

International, 1978, 38(l), 4637A.

Caroll, C.D. The relative effectiveness of three geometry

proof construction strategies, Journal for Research in

Mathematics Education, 1977, 8(1), 62-67.

Days, H., Wheatley, G.H. & Kulm, G. Problem structure, cognitive

level, and problem-solving performance. Journal for Research

in Mathematics Education, 1979, 10(2), 135-146.

Fennema, E. Mathematics. learning and the sexes: a review.

Journal for Research in Mathematics Education, 1974, 5(3),

126-139.

Page 61: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

54

Fennema, E. Sherman, J. Sex-related differences in mathematics

achievement and related factors: a further study. Journal

for Research in Mathematics Education, 1978, 9(3), 189-203.

Hafner, A.J. Influence of verbalization in problem--solving.

Psychologicalreporte, 195?, 3, 360.

Jerman, M.E. Individualized instruction in problem-solving in

elementary school mathematics. Journal for Research in

Mathematics Education, 1973, 4(l), 6-19.

Johnson, D. A. Rising, G.R. Guidelines for Teaching Mathematics.

Belmont: Wadsworth, 1967.

Kantowski, M.G. Processes involved in mathematical problem-solving.

Journal for Research in Mathematics Education, 1977, 8(3),

163-180.

Kilpatrick, J. Analyzing the solution of word problems in

mathematics. Doctoral dissertation, Stanford University, 1967.

Krutetskii, V.A. The psychology of mathematical abilities in

schoolchildren. Chicago: University of Chicago, 1976.

Kulm, G. Bussmann, H. A phase-ability Qodol of mathematical

problem-solving. Journal for Research in Mathematics

Education, 1980, 11(3), 178-189.

LeBlanc, J.F. You can teach problem-solving. Arithmetic Teacher,

1977, 25(2) 16-20.

Lee, F.L. Analysis of cognitive strategies of problem-solving

process in mathematics and physics. M.A. (Ed.) thesis,

the Chinese University of Hong Kong, 1981.

Page 62: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

55

Lester, F.K. Ideas about problems-solving: a look at some

psychological research. Arithmetic Teacher, 1977, 25(2), 12-15

Lester, F.K. Research on mathematical problem-solving. In National

Council of Teachers of Mathematics: Research in Mathematics

Education. Reston, V.A.: the Council, 1980.

Lucas, J.F. The teaching of heuristic problem-solving strategies

in elementary calculus. Journal for Research in Mathematics

Education, 1974, 5(1), 36-46.

Meyer, R.A. Mathematical problem-solving performance and intellecual

abilities of fourth grade children. Journal for Research in

Mathematics Education, 1978, 9(5), 334-348.

Meyer, R.E.. Thinking and Problem-solving. Glenview, Ill.: Scott,

Foresrnan, 1977.

Newell, A Simon, H.A. Human problem solving. Englewood Cliffs,

N.J.: Prentice-Hall, 1972.

Polyp, G. How to solve it (2nd edition). New York: Doubleday,

1957.

Post, T.R. Brennan, M.L. An experimental study of the effectiveness

of a formal versus informal presentation of a general

heuristic process on problem-solving in tenth grade geometry.

Journal for Research in Mathematics Education, 1976, 7(1),

59-64.

Robinson, M.L. An investigation of problem-solving behavior and

cognitive and affective characteristics of good and poor

problem-solvers in sixth grade mathematics. Dissertation

Abstracts International, 1973, 33, 5620A.

Page 63: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions

56

Roth, B. The effects of overt verbalization on problems-solving.

Dissertation Abstracts International, 1966, 27, 957B.

Sanders, V.A. Arithmetic problem-solving strategies of fourth

grade children. Di$sertation Abstracts International, 1973.

33(11), 5983A.

Scandura, J.M. Problem solving: a structural/process approach

with instructional implications. New York: Academic Press,

1977.

Silver, E.A. Student perceptions of relatedness among

mathematical verbal problems. Journal for Research in

Mathematics Education, 1979, 10(3), 195-210.

Suydam, M.N. & Weaver, J.F. Research on problem-solving:

implications for elementary school classroom. Arithmetic

Teacher, 1977, 25(2), 40-45,

Troutman, A.P. & Lichtenberg, B.P. Problem-solving in the

general mathematics classroom. Mathematics Teacher, 1974,

67(7), 590-597.

Vora, K. The effects of three instructional strategies on

problem-solving behaviors in secondary school mathematics.

Journal for Research in Mathematics Education, 1976, 7(5),

264-275.

Webb, L.W. Processes, conceptual knowledge and mathematical

problem-solving ability. Journal for Research in Mathematics

Education, 1975, 10(2), 83-93.

Wheatley, C.L. Calculator use and problem-solving performance.

Journal for Research in Mathematics Education, 1980, 11(5),

323-333.

Page 64: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions
Page 65: HEURISTIC STRATEGIES IN GEOMETRICAL PROBLEMSOLVING … · quadratic equation by formula are examples of algorithmic. Heuristics are procedures or outlines guiding the search for solutions