Usability EngineeringUsability Engineering

Dr. Dania Bilal

IS 592

Spring 2005

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What Is Usability Engineering?What Is Usability Engineering?

Measures multiple components of the user interface

Addresses the relationships between system and its users

Focuses on the HCI field

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What Is Usability Engineering?What Is Usability Engineering?

Bridges the gap between human and machines

Measures the quality of a system in relation to its intended users

Involves several methods, each applied at appropriate time of the design and development process

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Importance of UsabilityImportance of Usability

The sooner problems are found, the less expensive it is to fix them– Saves money by reducing designers’

and developers’ time

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Importance of UsabilityImportance of Usability

Learn more about users, tasks, expectations, successes, failures, information seeking, etc. and take these into consideration in redesigning a system or designing new one

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FactsFacts

People cannot find information on the Web about 60% of the time (User Interface Engineering)

Best Web site are usable only 42% of the time (Elizabeth Millard)

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FactsFacts

50% of potential sales over the Web are lost because users cannot find information sought; 40% do not return to a site when their first visit is negative (Forrester Research)

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FactsFacts

62% of Web shoppers give up looking for items to buy online due to not finding needed information and difficulty to use a site (Zona Research)

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Usability AttributesUsability Attributes

As described by Neilsen– Learnability– Efficiency–Memorability– Errors & their severity– Subjective satisfaction

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LearnabilityLearnability

The system must be easy to learn, especially for novice users.– Hard to learn systems are usually

designed for expert users.– There is a learning curve for novice and

expert users

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EfficiencyEfficiency

The system should be efficient to use so that once the user has learned how to use it, the user can achieve a high level of productivity.– Efficiency increases with learning about

the system

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MemorabilityMemorability

The system should be easy to remember, especially by casual users, so that they do not have to learn it all over again after a period of not using it.

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Errors Errors

The system should have a low error rate and should provide the user with a recovery mechanism from errors.–Minor errors–Major errors

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Minor ErrorsMinor Errors

User was able to recover from them– through system feedback– through awareness of error made

Errors that did not greatly slow down the user’s interaction with the system

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Major ErrorsMajor Errors

Difficult to recover from themLead to faulty work especially if they

are high in frequencyMay not be discovered by the user– These errors can be catastrophic

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Subjective SatisfactionSubjective Satisfaction

The system should be likeable by users

Satisfaction varies with kind of system used (educational vs. entertainment)

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RulesRules

The designer’s best guess is not good enough The user is always right The user is not always right Users are not designers Designers are not users More features are not always better Minor interface details matter Online help does not really helpSource: Nielsen, J. (1993). Usability Engineering.San Diego: Morgan

Kaufman.

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FactorsFactors

Address the functionality of the system vis-à-vis:– user needs– user tasks– user information seeking – user expectations– user cognitive processes

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Usability TestingUsability Testing

Part of the process of usability engineering

Involves users in the evaluation of a system by testing it

Goal– to uncover problems and correct them

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Usability EvaluationUsability Evaluation

Conducted at many stages during and after the system design and development process.

Employs various methods

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MethodsMethods

Cognitive walkthroughFocus groupsPrototypingTask analysisInspectionUser testing

http://www.usabilityfirst.com/methods

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Usability HeuristicsUsability Heuristics

http://www.useit.com/papers/heuristic/heuristic_list.html for usability principles

http://www.useit.com/papers/heuristic/heuristic_evaluation.html for how to conduct a heuristic evaluation

http://www.uie.com/articles

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Usability TestsUsability Tests

Stages– Preparation– Introduction– Test itself– Debriefing

Neilsen, J. (1993). Usability Engineering. San Diego: Morgan Kaufman.

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PreparationPreparation

Preparation for the experiment and data collection– Location of test (e.g., room to be used)– System to be used, capturing software,

etc.– Test materials, instructions,

questionnaires to be completed, as applicable

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IntroductionIntroduction

Test introduction includes– Purpose of the test– Test results to be used to improve

interface– Confidentiality of results & IRB– Explanation of software and equipment

used to collect data

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IntroductionIntroduction

– Users to ask clarifying questions anytime before and during the experiment

– Users to report problems and difficulty in using system during experiment (e.g., screen freeze)

– Verbal instructions, as applicable Introduction

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Running the TestRunning the Test

Experimenter(s) should refrain from interacting with users (e.g., personal opinions should not be expressed)

Experimenter(s) guide(s) observers. Both groups should refrain from making obtrusive comments during the experiment

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DebriefingDebriefing

User is debriefed after the test and may be asked to make comments or suggestions– verbally (via individual interview)– by completing a questionnaire

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DebriefingDebriefing

Experimenter ensures that files are collected with correct labeling; checks captured data files, questionnaires, etc.

Experimenter may write a brief preliminary report while events are still fresh.