Usability Goals and Specifications

HOW TO DEVELOPUSABILITY GOALS

version 1.0, May 24, 1996

U s a b i l i t y G o a l s

A Usability Goal is a

What is a usability goal?

A usability goal is a measurable design objective for how usable a system needs to be. A meaningfully stated usability goal is one that succeeds in communicating a product team’s intent, with as little ambiguity as possible, to deliver a usable system.

Usability goals written in good form have three identifiable components:

Performance What should the user be able to do?

Conditions Under what conditions should the user be able to do it?

Criteria How well must it be done?

Anatomy of a usability goal

The AME audience can create a complete proposal based on a completed solution using only the following:

MTC 2.0 XDoG (Xerox Document Generator )

A personalized template based on a Xerox standard template

On-line help

To be considered complete, the generated proposal must include:

Executive Summary

Table of Contents

Configuration & Prices

Terms and Conditions

Kinds of usability goals

Absolute: Logon must take no more than 7 seconds by the third try.

Relative: Logon must be faster on the new system than on the old system.

© 1996, Usability Analysis & Design, xEROX cORPORATION

Set of users this goal applies to.

Performance

Criterion

Conditions

Criteria defined further

version 1.0, May 23, 1996 How to Develop Usability Goals

Priority of Usability Characteristics

To say that we want the system to be “easy to use” can have many definitions. To help us think about the different meanings of usability, we use the following definitions of usability characteristics:

Usability Characteristic Definition

Memorability Ability for users to come back to the system and remember how to use it once they’ve been away from it for some time.

Learnability Ability for users to learn the system easily.

Efficiency of use once the system has been learned

Ability for users to save time in their work once they’ve learned the system.

Error recovery & prevention When the system presents an error message to users, it gives enough information for them to be able to continue with their work. Better yet, the system helps to prevent errors.

Subjective user satisfaction Users’ overall feelings about the system. Is it pleasant to use?

Rationale for Usability Characteristic Ratings by Audience

If you have more than one audience for your product, work through priorities for each of the audiences and have separate usability goals for each audience. This way, you will be able to see clearly the tradeoffs that you will need to make with respect to usability.

Benchmark tasks performed by users

For each audience, list the benchmark tasks that the audiences may need to perform using the system. Use the benchmark tasks as the performance for the usability goals, then add conditions and criteria.

Examples of usability goals

Efficiency & Learnability Working with only the MTC 2.0 interface and on-line help, the agent audience can perform at a minimum the following tasks within the 2nd use of the system and without having to go more than one level of detail beyond primary call queue window:

Research the establishment information

Make a call

Enter changes to customer (establishment-, contact-, and equipment-level) information

Code the disposition of the establishment at the close of the call

Subjective User SatisfactionGiven training and 2 weeks using the system, 3 out of 5 agents surveyed indicate that MTC 2.0 is satisfactory to use for key tasks.



EfficiencyThe AME audience can create a complete proposal based on a completed solution using only the following:

MTC 2.0 XDoG (Xerox Document Generator)

A personalized template based on a Xerox standard template

On-line help

To be considered complete, the generated proposal must include:

Executive Summary

Table of Contents

Configuration & Prices

Terms and Conditions

MemorabilityGiven standard training, a sales manager can generate an end-of-month “roll-up” report on the first try, using MTC 2.0 without having to consult on-line help and without an error.

Error Recovery & PreventionWhile using the system, a user can recover from an error by using only on-line help to resolve the problem.

Process for setting usability goals

1. Collect benchmark tasks, information about the audiences, and audience priorities for usability characteristics.

2. Collect information about what measurements are already in place.

3. Analyze the priorities by audience; and compare to team members’ assumptions. Decide on priority order for usability characteristics.

4. Decide which benchmark tasks are most relevant to the priorities of the audiences and the usability characteristics. Set these as the performance.

5. Write in the conditions under which the audience will need to perform the benchmark tasks. Write in the criteria.

6. Have team review and accept the usability goals.

7. When faced with design decisions, review the usability goals.

8. Measure progress toward usability goals during design iterations.

Questions to ask about usability goals

What process will you use to measure the goals?

Are there resources to measure the goals?

Are the users specified clearly enough?



Do all project members agree on each goal?

Does the goal match the size and scope of the project?

Using usability goals during design

Refer to usability goals during design to help with prioritizing design tradeoffs.

How can you measure your progress toward usability goals?

Usability testing

Surveys

Make sure that the goals match the method in which you will evaluate whether they are met.

How can Usability Analysis & Design help you with usability goals?

Usability goal workshop

Review of goals

Consulting with your team

Best references and further reading

Bennett, J., Holtzblatt, K., and J. Whiteside. “Usability Engineering: Our Experience and Evolution,” in Handbook of Human-Computer Interaction. ed. Hellander. Elsevier Science Publishers, Amsterdam. 1987.

Mager, R., Preparing Instructional Objectives. 2nd ed. David S. Lake Publishers: Belmont, CA. 1984.

Nielsen, J. “The Usability Engineering Life Cycle.” Computer. March 1992.


Usability Goals and Specifications

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