Usability Introduction

Andrew Wadsworthguest lecture for

LIS390-W1A

Design

the act of working out the form of something

an arrangement scheme something intended as a guide for making

something else a preliminary sketch indicating the plan for

something

Design… as a process The approach that engineering (and some other)

disciplines use to specify how to create or do something. A successful design must satisfies a (perhaps informal) functional specification (do what it was designed to do); conforms to the limitations of the target medium (it is possible to implement); meets implicit or explicit requirements on performance and resource usage

Interface

a common boundary between two things a program that controls a display for the

user (usually on a computer monitor) and that allows the user to interact with the system

A boundary across which two systems communicate.

User Interface

a program that controls a display for the user (usually on a computer monitor) and that allows the user to interact with the system

The aspects of a computer system or program which can be seen (or heard or otherwise perceived) by the human user, and the commands and mechanisms the user uses to control its operation and input data.

Usability

The effectiveness, efficiency, and satisfaction with which users can achieve tasks in a particular environment of a product. High usability means a system is: easy to learn and remember; efficient, visually pleasing and fun to use; and quick to recover from errors.

Human-Computer Interaction

(HCI) The study of how humans interact with computers, and how to design computer systems that are easy, quick and productive for humans to use.

System Acceptability

Practical Acceptabilityo Costo Compatibilityo Reliabilityo Usefulness

Social Acceptability

Usefulness

UtilityUsability

o Easy to learno Efficient to useo Easy to remembero Few Errorso Pleasing to use

Components of Usability

LearnabilityEfficiencyMemorabilityErrorsSatisfaction

LearnabilityCharacteristics

o easiest component to measureo some systems take zero time to learn

Measuremento time to complete a task successfullyo a set of tasks in a minimum period of time

Considerationso most users don’t take the time to completely learn the

system before they begin to use it

Efficiency of Use Characteristics

o refers to when a user’s level of performance no longer increases over time (levels out)

o users may never reach the steady-state performance level (always increasing)

o most users plateau once they have learned “enough” Measurement

o must have access to experienced userso at steady-state level where performance no longer

increases Considerations

o must determine expertise level for the system to get a representative sample of users

Memorability

Characteristicso casual users only intermittent user of a system,

but are familiar with ito they don’t need to learn from scratcho improvements in learnability often make a

interface easy to remembero not tested as much as other components

MemorabilityMeasurement

o casual users away from the system for a period of time, then measure the time it takes to complete tasks

o after an initial user test, ask users questions about the system and have them explain the effect of commands or the name of the command

Considerationso casual users typically apply to utility software

Errors – Few or Catastrophic

Characteristicso we want to get low error rates for userso an error is any action that does not accomplish

the desired goal towards the completion of a task

Errors – Few or CatastrophicMeasurement

o count the number of incorrect actions made by users while performing a task

o incorrect actions may only slow a user o some errors effect time only and thus relate to efficiencyo catastrophic errors, not discovered by the user, lead to

bad results or incompletion of the task

Considerationso separate simple errors from catastrophic errors

Satisfaction (subjective)Characteristics

o how pleasant it is to use the systemo subjective and biasedo there are many ways to measure

Measuremento ask the user about their experience – usually via

short questionnaire at the end of testo collect objective data and extract subjective

preferences of the usero EEG’s, pupil dilation, heart rate, etc.

Satisfaction (subjective)

Considerationso Attitudes toward computers can impact

attitudes towards a systems usabilityo For some systems it’s more important to be

enjoyable to the user rather than fast to learn and use (ie, games)

Accelerators

Are interface elements that allow users to perform frequent tasks quickly

Most useful as users gain expertise with the system

Novice into Experts

A novice who is performing highly and begins to switch over and use accelerators may experience a temporary performance dip

Usability Considerations

User TestingUser’s individual characteristics and

differenceso Must consider both when testing usabilityo “know thy user”, try to classify them

Other Usability Considerations

show shortcuts with menu items to assist users and promote accelerators

online help with examples and links for further research

short menus (for novice users), long menus (for expert users)

Concluding Thoughts

previous experience with similar interfaces really helps using and learning other systems

more knowledge in the specific domain will greatly effect a users ability to know what a system is all about

users are not designers, simply providing only custom interfaces based on the users preference doesn’t work well

Simple Usability Testing

In a usability test, one user at a time is shown a Web site (prototype, screen shots, print-outs) and asked to:o Figure out what it iso Try to use it to do a typical task or set of

tasks

Usability Testing Truisms

1. "There is no such thing as a bad usability test."

2. One test is better than none.3. Test early, test often.4. 5 users will uncover 85% of usability

problems.5. Shoe-string usability testing is still

usability testing.

Usability Testing

What to testo "Get it"- purpose, value, how it's organized,

how it workso Task - ask the user to do something and

observe

Usability Testing

How to testo Determine the specific tasks and parts of the

site you will be testing. Carefully think through your instructions (don't reveal answers with your questions). Write out a script.

Usability TestingHow to test

o Test your test. Try it yourself.o "We are testing the site, not you."o Encourage users to think out loud. Ask them

again.o Questions. Answer questions with questions

not explanations.o Keep instructions simple.o Ask more questions.o Report what you saw.

Usability Testing

Test Summaryo Review what you learned. o Figure out what needs to be fixed and how to

fix it. o Usability testing will give a wealth of data,

the trick is determining what to act on. o Focus on specific issues, tweak before

redesigning.

Usability Testing

Test Summaryo The most common issues you encounter will

be users that are: • "unclear on the concept“

• labels that don't mean what you intended

• too much or too little information accompanying your content and interactions

o Resist adding "features" and make sure you tackle the "big stuff".

Types of Usability Tests

Exploratory TestAssessment TestValidation TestComparison Test