There are times when user experience practitioners might consider using the System Usability Scale (SUS), but there is an item that just doesn’t work in their context of measurement. For example, the first item is “I think I would like to use this system frequently.” If the system under study is one that would only be used infrequently, then there is a concern that including this item would distort the scores, or at best, distract the participant. The results of the current research show that the mean scores of all 10 possible nine-item variants of the SUS are within one point (out of a hundred) of the mean of the standard SUS. Thus, practitioners can leave out any one of the SUS items without having a practically significant effect on the resulting scores, as long as an appropriate adjustment is made to the multiplier (specifically, multiply the sum of the adjusted item scores by 100/36 instead of the standard 100/40, or 2.5, to compensate for the dropped item).
