A Completion Rate Conundrum: Reducing bias in the Single Usability Metric

Abstract

In the Single Usability Metric benchmarking method, the calculation of completion rates creates a bias for completion rates by ignoring the z-score transform that is conducted for satisfaction and time-on-task measures. This artificially inflates all ‘good’ scores and marks some ‘poor’ scores as ‘good’. This paper discusses two methods to augment the SUM so that it will accurately calculate completion rates into the final SUM score.