The use of precision of software development effort estimates to communicate uncertainty

Abstract

The precision of estimates may be applied to communicate the uncertainty of required software development effort. The effort estimates 1000 and 975 work-hours, for example, communicate different levels of expected estimation accuracy. Through observational and experimental studies we found that software professionals (i) sometimes, but not in the majority of the examined projects, used estimate precision to convey effort uncertainty, (ii) tended to interpret overly precise, inaccurate effort estimates as indicating low developer competence and low trustworthiness of the estimates, while too narrow effort prediction intervals had the opposite effect. This difference remained even when the actual effort was known to be outside the narrow effort prediction interval. We identified several challenges related to the use of the precision of single value estimates to communicate effort uncertainty and recommend that software professionals use effort prediction intervals, and not the preciseness of single value estimates, to communicate effort uncertainty.