Usability

Usability is the measure of the quality of a user's experience when interacting with a product or system. Usability is a combination of factors that affect this experience, including:

• Ease of Learning - How fast can a user who has never seen the user interface before learn it sufficiently well to accomplish basic tasks?
• Efficiency of Use - Once an experienced user has learned to use the system, how fast can he or she accomplish tasks?
• Memorability - If a user has used the system before, can he or she remember enough to use it effectively the next time or does the user have to start over again learning everything?
• Error Frequency and Severity - How often do users make errors while using the system, how serious are these errors, and how do users recover from these errors?
• Subjective satisfaction - How much does the user like using the system?

Usability Testing

The goal of usability testing is to ascertain what will help users accomplish their tasks and what may impede them. Using the prototype as a starting point, the usability testers build a set of scenario tasks they will ask users to attempt. As detailed information about user success is gathered and reported, the prototype can be modified and additional aspects of that prototype tested.

Usability testing can be done inexpensively or more formally, depending on the size and budget of the site under development. When the site has been implemented, it is incumbent on the developers or the owners of the content to assess its performance by analyzing reports, usage logs, and other data sources for the site and by continuing to gather user feedback on usability.

(Copyright 2006. U.S. Department of Health and Human Services. )

Related Resources

• Useit.com - Jakob Nielson
• User Interface Engineering - Jared Spool
• Usability.gov - US Department of Health & Human Services