MIS - Usability & Cognitive Engineering

8/3/2019 MIS - Usability & Cognitive Engineering

http://slidepdf.com/reader/full/mis-usability-cognitive-engineering 1/43

Management Information Systems

Usability & Cognitive Engineering

Prof. Rushen Chahal

Prof. Rushen Chahal



The design principles for usability

(Gould & Lewis, 1985)

1. Early focus on the users

2. Empirical measurement

3. Iterative design

4. Integrative design (help, training, documentation, etc

in parallel).

Prof. Rushen Chahal



Usability

± 1. Early focus on users

bring the design team into direct contact with the users

right from the start

get the user involved so they can instill their knowledgeinto the design process

Prof. Rushen Chahal



Usability

± 2. Empirical measurement

actual behavioral measures of

± learnability

± usability

testing of appropriate task or concepts memory access

speeds, time to learn the function keys remember

novices are different form experts.

collect the user thoughts (use protocol analysis)

collect the user's mistakes

collect the user's attitudes

Prof. Rushen Chahal



Usability

± 3. Iterative design

incorporate the results from the tests into the next

prototype

set goals for the system

an evaluation criteria

± easy to use

± user friendly

± easy to operate ± simple

± responsive

± flexible

this is feedback and evaluationProf. Rushen Chahal



Usability

± 4. Integrated design

build help, training, documentation, process modules at

the same time.

Prof. Rushen Chahal



Usability Definitions

Usability is task related, people related and

function related. It has cognitive, behavioral,

and communicative components.

To be truly usable a system must be

compatible not only with the characteristics of

human perception and action but, and most

critically, with user's cognitive skills in

communication, understanding, memory and

problem solving." (Hammond, 1981)

Prof. Rushen Chahal



Usability Definitions

Designing a usable system requires:

± understanding of the intended users.

±the amount of time they expect to use the system.

± how their needs change as they gain experience.

± (Goodwin, 1987)

Prof. Rushen Chahal



Usability Design

± 1. Early focus on the user

What: understand the user's cognitive, behavioral,

attitudinal - and goals of the organization

How: interviews, observations, discussions, workingwith the users.

± 2. Empirical Measurement

What: Tasks and dependent measures.

How: Testing - protocol analysis, observation,

interviews, etc.

Prof. Rushen Chahal



Usability Design

± 3. Interative design

What: The problems encountered are to be corrected

and measure again.

How: An evolving system - prototyping.

± 4. Integrated Design

What: a parallel development of interface, help,

documentation, training and measurement.

Gould & Lewis, 1985, Gould, et al. 1991Prof. Rushen Chahal



Measurable Human

Factors Goals (Usability) ± Time to learn - How long does it take for typical

members of the target community to learn to use

the commands relevant to a set of tasks?

± Speed of performance - How long does it take to

carry out the bench set of tasks?

± Rate of errors by users - how many and what kinds

of errors are made in carrying out the benchmark

set of tasks?

Prof. Rushen Chahal



Measurable Human

Factors Goals (Usability) ± Subjective satisfaction - How much did the users

like using aspects of the system?

± Retention over time - How well do users maintain

their knowledge?

Shneiderman, B., Designing the User Interface, 14

Prof. Rushen Chahal



Cognitive Engineering

Learning is a relatively permanent change in behavior

resulting from conditions of practice

Human learning then is the association of one item

with another item, paired associated learning pairs of stimuli come in, a mental association is made

for them, and the stimuli then become interrelated

Future learning can then depend upon past learning.

People develop new cognitive structures by usingmetaphors to cognitive structures they have already

learned

Prof. Rushen Chahal




The metaphor is a model or structure or conceptual

framework which help bridge any gap between what

the person (user) knows and what is being attempted

to be learned.

metaphors spontaneously generated by users will

predict the ease with which they an master a computer

system

If this is indeed the case then systems designers must

understand and employ the use of metaphors in system

designs

Prof. Rushen Chahal




± Carroll and Thomas (1982) developed eight

recommendations to aid both the user and

designer in build effective systems

1. Find and use appropriate metaphors in teaching thenaive user a computer system. A metaphor to be useful

must have a suitable domain for a given system and

given user population.

2. Given a choice between two metaphors chose theone which is most congruent with the way the system

works.

Prof. Rushen Chahal




3. Assure that the correct attitude is presented. Costs of

ignoring this recommendation range from user

dissatisfaction and reduced productivity to sabotage.

4. When more than one metaphor is need to represent asystem, choose metaphors that are similar enough, but not

to similar that confusion results.

5. Consider the probable consequences to users and

system designers of each metaphor used. This is the

evolving state from novice to user. Two path are possible:

one leading to directly to the system, the other to a new

metaphor.

6. The limits of the metaphor should be pointed out to the

user. Prof. Rushen Chahal




7. The intent of the metaphor in the beginning is to aid

understanding and usability; for the continual user, it is no

longer necessary. The metaphor is used also as a

motivator, at first to get the user to use the system, then tomake him productive and keep his interest.

8. Provide the user with an exciting metaphor for routine

work and eventually present the user with advanced

scenarios requiring different action.

Prof. Rushen Chahal




± Learning is a relatively permanent change in

behavior resulting from:

Elaboration, association, practice, rehearsal.

± Metaphor - a mental model, structure, or

framework which help bridge any gap between

what a person knows and what is being attempted

to be learned.

Prof. Rushen Chahal




(goals) ± To understand the fundamental principles of

human action and performance relevant to the

principles of system design.

± To devise physical systems that are pleasant to

use.

±Psychological variables - goals, intentions andattitudes

± Physical variables - pertain to to system.

Prof. Rushen Chahal






Molich and Nielsen (1990) nine basic categories of usability

problems:

± 1. Simple and Natural Dialogue: The dialogue should be simple

and clearly stated. It should not contain any irrelevant

information. The information should appear in a natural and

logical order.

± 2. Speak the User's language: The dialogue should be expressed

in the terminology familiar to the user rather than in system

oriented terms.

Prof. Rushen Chahal




± 3. Minimize the User's Memory Load: Instructions should be

visible, easily retrievable, and simplified. Information presentation

load should be reduced when ever possible (i.e., users should not

have to remember file names when they are retrievable).

± 4. Be Consistent: The terminology and concepts should always beused in the same manor.

± 5. Provide Feedback: The system should provide feedback as to

what is transpiring within a reasonable time.

± 6. Provide Clearly Marked Exits: Clearly marked exists should be

provided to the user in case of mistakes.

Prof. Rushen Chahal




± 7. Provide Shortcuts: System flexibility for the novice and expert.

Menus for the novice and commands for the experts.

± 8. Provide Good Error Messages: The error messages should be

constructive and provide meaningful suggestions to the user of

what to do next.

± 9. Error Prevention: A careful design that prevents error

messages form occurring in the first place.

Prof. Rushen Chahal




± Conclusion:

± the identification of specific, and potential usability problems in a

human computer dialogue design is difficult.

±usability goals be defined and incorporated into the design.

± designers may have difficulties in applying the principles of Gould

and Lewis (1985) unless they have simple basic requirements for

the design product

± This statement draws attention to the first principle from Gould

and Lewis (1985), early focuses on the user

Prof. Rushen Chahal




± In this respect the design team defines the application and

measures of usability

± The nine principles were derived from experience and then

analyzed a posterior from a survey.

± these nine measures are analyzed for graphical interfacedesigns and are even more important since graphical

interfaces increase the degrees of freedom by orders of

magnitude.

± also suggests that no single interface principle can be

absolute, there is a need for trade-offs. ± the user team define what is need, let the system evolve and

measure usability.

Prof. Rushen Chahal




± The major differences between Molich and Nielsen (1990),

and Gould and Lewis (1985) are three fold.

± 1. Gould and Lewis are defining usability as a set of rules an

principles which are subject to the needs of the user and the

tasks; the usability measures are defined in this context and;there is an iterative cycle for development.

Prof. Rushen Chahal




± 2. Molich and Nielsen (1990) and Nielsen (1990) are applying

the usability measures to systems that are not in the design

phase (a posterior analysis).

± 3. Gould and Lewis are a priori.

Prof. Rushen Chahal




± Summary:

The objective of the metaphor is to add psychology to

the user interface

In designing a human computer interface the designermust implicitly build in a psychological (mental or

cognitive) model of the system

The usability of the system then depends upon the

users mental model and the designers projection of

what the users mental model should be

The smaller the distance the greater the usability.

Prof. Rushen Chahal




± Summary (cont)

usability is the distance between the design model and

mental model, the smaller the distance the greater the

usability The interface is what bridges the gap, the more it

responds the way the user' mental picture says it

should, the more usable it is.

Prof. Rushen Chahal



Prof. Rushen Chahal



Prof. Rushen Chahal



Prof. Rushen Chahal



Gulf of

Execution

of Execution

Prof. Rushen Chahal



Prof. Rushen Chahal



Prof. Rushen Chahal



Gulfs

Gulf of Execution: Bridged by ± Psychological

Metaphor, intentions, practice

± Physical

The interface design

Gulf of Evaluation: Bridged by

± Psychological

Comparisons between goals and expectations (formed

attitudes, cognitive dissonance)

± Physical

proper output interfaceProf. Rushen Chahal



Prof. Rushen Chahal




± Brown and Newman (1985) have suggested that

are five main issues to understanding system

usability:

1. System opacity- Computer based systems areopaque, there function can not be perceived from their

structure.

2. System complexity- Computer based system allows

the users to access and manipulate many processessimultaneously.

Prof. Rushen Chahal




3. Social complexities- Differences in perceived values

and styles brought about either though cultural or

individual expectations.

4. Lack of appropriate metaphor- An inappropriate

model of the system either mental (user) or design.

5. Interactivity and ambiguity- The goals, intention or

purpose of the system, interface, or output not defined

clearly.

Prof. Rushen Chahal




± Brown and Newman (1985) recommend an

integrative approach

used to design

used to implement computer based systems

Prof. Rushen Chahal




± Brown and Newman (1985) recommend an

integrative approach (cont)

This approach includes:

± 1. the development of mental models and metaphors to aid inunderstanding.

± 2. communicative repair which is used in iterative testing and

modification.

± 3. training strategies which is an integrated parallel approach.

± 4.setting the organization goal and objectives which is theearly focus on the user.

Prof. Rushen Chahal



Cognitive definitions

Usability is the distance between the design

model and mental model, the smaller the

distance the greater the usability.

How?

Prof. Rushen Chahal



Cognitive definitions

Brown & Newman(1985)

Gould & Lewis (1985)

Develop mental models Early focus on users

Communicate Iterative testingMeasure Measurement

Set goals & objectives Integrative

Prof. Rushen Chahal

Documents

MIS - Usability & Cognitive Engineering