Recommended methods: 9. Usability testing
To identify usability problems and obtain measures of usability.
- Major usability problems are identified, including problems related to the specific skills and expectations of the users.
- Measures can be obtained for the users' effectiveness, efficiency and satisfaction.
- It is important that the users, tasks and environment used for the test are representative of the intended context of use.
- Select the most important tasks and user groups to be tested.
- Select users who are representative of each user group. 3-5 users are sufficient to identify problems. 8 or more users of each type are required for reliable measures.
- Produce a task scenario and input data and write instructions for the user (tell the user what to achieve, not how to do it).
- Plan sessions allowing time for giving instructions, running the test, answering a questionnaire, and a post-test interview.
- Invite developers to observe the sessions. If developers cannot be present, videotape the sessions, and show developers edited clips.
- Two administrators are normally required: one to interact with the user, and one to note problems and to speak to any observers.
- If possible use one room for testing, linked by video to another room for observation.
- If usability measures are required, observe the user without making any comments.
- If measures are not required, prompt the user to explain their interpretation of the contents of each screen and their reason for making choices.
- Welcome the user, and give the task instructions.
- Do not give any hints or assistance unless the user is unable to complete the task.
- Observe the interaction and note any problems encountered.
- Time each task.
- At the end of the session, ask the user to complete a satisfaction questionnaire such as SUMI.
- Interview the user to confirm they are representative of the intended user group, to gain general opinions, and to ask about specific problems encountered.
- Assess the results of the task for accuracy and completeness.
- Produce a list of usability problems, categorised by importance (use post-it-notes to sort the problems), and an overview of the types of problems encountered.
- Arrange a meeting with the project manager and developer to discuss whether and how each problem can be fixed.
- If measures have been taken, summarise the results of the satisfaction questionnaire, task time and effectiveness (accuracy and completeness) measures.
- If a full report is required, the Common Industry Format provides a good structure.
There is a detailed example of a usability report using the Common Industry Format.
More information on usability testing can be found in the INUSE Handbook. The MUSiC Performance Measurement Method provides detailed instructions for measuring effectiveness, efficiency and satisfaction.
Expert evaluation can be used as an alternative, but without user testing there can be no certainty that the product will be usable.
Collect feedback from users after release to inform any redesign.
Copyright © 2002 Serco Ltd. Reproduction permitted provided the source is acknowledged.