Blog Topic: SUM

There is no usability thermometer to tell you how easy to use a website or software application is. Instead we rely on the outcomes of good and bad experiences which provide evidence for the construct of usability. Combining multiple usability metrics into a single usability metric (SUM) is something we proposed seven years ago[PDF] and

SUM is a standardized, summated and single usability metric. It was developed to represent the majority of variation in four common usability metrics used in summative usability tests: task completion rates, task time, satisfaction and error counts. The theoretical foundations of SUM are based on a paper presented at CHI 2005 entitled “A Method to