Severity ratings can be used to allocate the most resources to fix the most serious problems and can also provide a rough estimate of the need for additional usability efforts. If the severity ratings indicate that several disastrous usability problems remain in an interface, it will probably be unadvisable to release it. But one might decide to go ahead with the release of a system with several usability problems if they are all judged as being cosmetic in nature.

The severity of a usability problem is a combination of three factors:

• The frequency with which the problem occurs: Is it common or rare?
• The impact of the problem if it occurs: Will it be easy or difficult for the users to overcome?
• The persistence of the problem: Is it a one-time problem that users can overcome once they know about it or will users repeatedly be bothered by the problem?

Severity Ratings for Usability Problems