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"Web sites that are hard to use frustrate customers,
forfeit revenue and erode brands. New media executives can apply a disciplined
approach to improve all aspects of ease-of-use. Start with usability audits
to assess specific flaws and understand their causes. Then fix the right
problems through action-driven design practices. Finally, maintain usability
with changes in business processes."
- Forrester Research
Why most Web sites fail
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Developing Usability Goals
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?
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.
Priority of Usability Characteristics
To say a system to be “easy to use” can have many definitions. To help think about the different meanings of usability, use the following definitions of usability characteristics:
- 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: 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.
- 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 web site, 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 application interface and on-line help, the 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
- User Satisfaction
Given training and 2 weeks using the system, 3 out of 5 users surveyed indicate that application is satisfactory to use for key tasks.
- Efficiency
The audience can create a complete proposal based on a completed solution using only the following:
- System Document Generator
- A custom template (modified from a standard template)
- On-line help
- Memorability
Given standard training, a project manager can generate an end-of-project “roll-up” report on the first try, using the application without having to consult on-line help and without an error.
- Error Recovery & Prevention
While 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
- Collect benchmark tasks, information about the audiences, and audience priorities for usability characteristics.
- Collect information about what measurements are already in place.
- Analyze the priorities by audience; and compare to team members’ assumptions. Decide on priority order for usability characteristics.
- Decide which benchmark tasks are most relevant to the priorities of the audiences and the usability characteristics. Set these as the performance.
- Write in the conditions under which the audience will need to perform the benchmark tasks. Write in the criteria.
- Have team review and accept the usability goals.
- When faced with design decisions, review the usability goals.
- 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 evaluation method.
+ Return to Usability Test Planning
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