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 are used to classify problems. When you classify a problem as one of these levels you need to be able to explain your rationale.
0 = I don’t agree that this is a usability problem at all
1 = Cosmetic problem only: need not be fixed unless extra time is available on project
2 = Minor usability problem: fixing this should be given low priority
3 = Major usability problem: important to fix, so should be given high priority
4 = Usability catastrophe: imperative to fix this before product can be released