Ap psy methods, stats

Chapter 1: Thinking Critically with

Psychological Science

Aaron Biggar

AP Psychology

I. The Need for Psychological Science

98% Certainty

1. The area of the US in square miles?

2. The population of Afghanistan in 2001?

3. American battle deaths in Spanish-American War?

4. GM advertising budget in 1999?

5. Female officers in US Army in 2000?

98% Certainty

1. Area of US:

2. Afghan population:

3. Battle deaths:

4. GM advertising:

5. Female officers:

3.6 million sq. miles

26.8 million

385

$2.9 billion

9.953


A. Limits of intuition and common sense

1. Hindsight bias

2. Overconfidence


A. Limits of intuition and common sense

B. Scientific attitude

C. Scientific method

1. Theory & hypothesis

2. Operational definitions

3. Replication

4. Goals:

II. Description

II. Description

A. Case studies

B. Surveys (questionnaires & interviews)

1. Wording effects

72% interested in “plants & trees”39% interested in “botany”

62% whites agree “problems faced by blacks brought on by blacks themselves” (white interviewer)46% whites agree with black interviewer

A majority oppose an amendment “prohibiting abortions”A majority support “protecting the life of an unborn child”

1. Is the Mississippi River longer or shorter than 500 miles?

2. How many miles long is it?

1. Is the Mississippi River longer or shorter than 3000 miles?

2. How many miles long is it?

II. Description

A. Case studies


1. Wording effects

2. Samples & populations

a. False consensus & other biases

b. Random & representative techinques

II. Description

A. Case studies


C. Naturalistic observation & observer effects

III. Correlation

III. Correlation

A. Positive & negative

B. Scatterplots

III. Correlation


B. Scatterplots

C. Correlation coefficient (r)

III. Correlation


B. Scatterplots

C. Correlation coefficient (r)

D. Causation v. predictive value

Correlation between TV watching & GPA

III. Correlation

A. Positive & negativeB. ScatterplotsC. Correlation coefficient (r)D. Causation v. predictive value

E. Illusory correlationF. Order in random events

IV. Experimentation

IV. Experimentation

Purpose of an expt:

General hypothesis: food effects learning

Specific (operationalized) hypothesis: students who eat an oatmeal raisin cookie before class each day will have higher average scores on the semester final than students who don’t eat a cookie.

Eating cookies before class each day will lead to higher average scores.

Variables:Independent (IV)

Controlled by experimenterThe “cause” variable

Dependent (DV)Predicted by experimenterThe “effect” variable


Groups (conditions): to establish different levels of the IV

Experimental groupExposed to IVGet cookie

Control groupNot exposed to IVNo cookie

What if kids get cookies and A’s?


IV DV

Expt. Gp. Cookie 95%

Cntrl. Gp. No Cookie 82%

ConfoundingVariables

Environmental

Expectations

Individualdifferences

Random SamplingTo select participants from populationAllows you generalize results

Random AssignmentTo divide participants into groupsControls confounding variables


IV DV

Expt. Gp. Cookie 95%

Cntrl. Gp. No Cookie 82%

85%

93%

Statistical Significance

p value

likelihood a result is caused by chance

can be no greater than 5%

p ≤ .05

Replication

Non-replicated results are preliminary.

Linus Pauling (1970). Vitamin C prevents colds.

IV DV

Expt. Gp. Vit C

Cntrl. Gp. Placebo

Expt. Gp.45%

Fewer colds

Experimental Design Terms

• Hypothesis• Operational definitions• Participant selection• IV & DV• Experimental & control groups• Confounding variables• Random assignment• Placebo control• Double blind procedure• Statistical significance (p value)• Replication

Quasi-experiments

• Men are better drivers than women.

• Cigarette smoking causes lung cancer.

V. Statistical Reasoning


A. Describing data

1. Frequency distributions

13 A+ 40 13 A+12 A 39 4 41% A 12 23 52% 12 A 11 39%

38 11 A- 11 10 11 A- 1411 A- 37 11 B+ 10 15 10 B+ 910 B+ 36 6 B 9 5 41% 9 B 12 45%9 B 35 4 31% B- 8 6 8 B- 8

34 5 C+ 7 2 7 C+ 28 B- 33 5 C 6 1 5% 6 C+ 2 11%7 C+ 32 4 C- 5 5 C- 36 C 31 3 19% D+ 4 2 4 D+

30 3 D 3 3% 3 D 3 5%5 C- 29 2 D- 2 2 D-4 D+ 28 F 1 0% 1 F 0%3 D 27 4 8% 0

26 12 D- 251 F 24 2%

<24 1

Multiple Choice

Essay

Composite

Mean=34.3SD=4.2

Mean=10.2SD=2.0

Mean=9.3SD=2.3


A. Describing data

1. Frequency distributions

2. Histograms & frequency polygons

0

10

20

30

40

50

A B C D

Grades

Per

cen

tag

e o

f st

ud

ents

Histogram

0

10

20

30

40

50

A B C D

Grades

Per

cen

tag

e o

f st

ud

ents

Frequency Polygon


A. Describing data

B. Measures of central tendency

43544

Mode=most common=4

Mean=arithmetic average=20/5=4

Median=middle score=4

Central Tendency 1968 TOPPS Baseball Cards

Nolan Ryan $1500

Billy Williams $8

Luis Aparicio $5

Harmon Killebrew $5

Orlando Cepeda $3.50

Maury Wills $3.50

Jim Bunning $3

Tony Conigliaro $3

Tony Oliva $3

Lou Pinella $3

Mickey Lolich $2.50

Elston Howard $2.25

Jim Bouton $2

Rocky Colavito $2

Boog Powell $2

Luis Tiant $2

Tim McCarver $1.75

Tug McGraw $1.75

Joe Torre $1.5

Rusty Staub $1.25

Curt Flood $1

With Ryan:Median=$2.50Mean=$74.14

Without Ryan:Median=$2.38Mean=$2.85


A. Describing data


C. Measures of variation

1. Range

2. Variance & standard deviation

Standard DeviationPunt

Distance

36384145

Mean=160/4=40 yds

Deviationfrom Mean

-4-2+1+5

DeviationSquared

16 4 125

46

46/4=11.5=variance

std. dev.=

variance=

11.5=3.4 yds


A. Describing data



D. Characteristics of the normal curve

V. Statistical ReasoningA. Describing data



D. Characteristics of the normal curve

E. Inference

1. Does the sample represent the pop.?

a. Non-biased sample-good

b. Low variability-good

c. Larger samples-good

V. Statistical ReasoningE. Inference

1. Does the sample represent the pop.? 2. Are differences between groups

statistically significant?

a. Big differences-good

b. Low variability-good

c. Big groups-good

VI. FAQs

VI. FAQs

A. Can lab expts illuminate real life?

B. Does behavior depend on one’s culture?

C. Does behavior vary with gender?

D. Why do psychologists study animals?

E. Is it ethical to experiment on animals?

F. Is it ethical to experiment on people?

G. Is psychology free of value judgments?

H. Is psychology potentially dangerous?

VI. FAQs

F. Is it ethical to experiment on people? Yes, if the APA’s ethical guidelines are

followed.

1. Informed consent

2. Protection from harm

3. Confidentiality

4. Debriefing

How should participants be chosen?

• Good answers use and make clear your understanding of the terms “sample” and “population.”

• Good answers explain how to draw a random sample.

• Ex. “All the assembly line workers for a company could be the population. I would draw a random sample of 40 of them by picking names from a hat.”

Create operationalized hypothesis

• Good answers make an educated guess (“Workers who are complimented will work harder”)

• Good answers develop specific, measurable ways to define compliments and hard work.

• Ex. “10 compliments will be given at 4 specific times.” “Supervisors will give compliments from a pre-developed list.” “Hard work will be measured by using the number of items produced each hour.”

Identify IV & DV

• IV=compliments

• DV=work effort

• Do not propose a direction when stating the variable (“the DV is an increase in work.”)

• People are never the variables (“the IV is the people who get complimented.”)

Describe the groups

• Experimental group gets compliments.

• Control group doesn’t get compliments.

• Use the terms!

Confounding variables

• Do not confuse random assignment with random sampling.

• Be reasonable!!!

• “The company policy will be to have people sleep in a hotel with no TV or radio.”

• “I will provide a seminar on the importance of sleep.”

• “All workers must be paid the same.”

Documents

Ap psy methods, stats