Table 2.

Rolf Molich's severity rating scale.

Five-point severity rating scale	Description of severity ratings
(0) Improvement	Which does not substantially disturb the user's experience
(1) Minor problem	The user will be somewhat delayed (few minutes)
(2) Severe problem	The user will be much delayed (several minutes)
(3) Critical problem	The user cannot carry out the task
(4) Malfunction problem	The system does not work properly