SUS: A Quick and Dirty Usability Scale

Usability does not exist in any absolute sense; it can only be defined with reference to particular contexts. This, in turn, means that there are no absolute measures of usability, since, if the usability of an artefact is defined by the context in which that artefact is used, measures of usability must of necessity be defined by that context too. Despite this, there is a need for broad general measures which can be used to compare usability across a range of contexts. In addition, there is a need for “quick and dirty ” methods to allow low cost assessments of usability in industrial systems evaluation. This chapter describes the System Usability Scale (SUS) a reliable, low-cost usability scale that can be used for global assessments of systems usability. Usability and context Usability is not a quality that exists in any real or absolute sense. Perhaps it can be best summed up as being a general quality of the appropriateness to a purpose of any particular artefact. This notion is neatly summed up by Terry Pratchett in his novel “Moving Pictures”: “ ‘Well, at least he keeps himself fit, ’ said the Archchancellor nastily. ‘Not like the rest of you fellows. I went into the Uncommon Room this morning and it was full of chaps snoring!’ ‘That would be the senior masters, Master, ’ said the Bursar. ‘I would say they are supremely fit, myself.’ ‘Fit? The Dean looks like a man who’s swallered a bed!’ ‘Ah, but Master, ’ said the Bursar, smiling indulgently, ‘the word “fit”,as I understand it, means “appropriate to a purpose”, and I would say that the body of the Dean is supremely appropriate to the purpose of sitting around all day and eating big heavy meals. ’ The Dean permitted himself a little smile. “ (Pratchett, 1990) In just the same way, the usability of any tool or system has to be viewed in terms of the context in which it is used, and its appropriateness to that context. With particular reference to information systems, this view of usability is reflected in the current draft international standar