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.