Improved measurement of software development effort estimation bias

•An effort estimate is the estimate of a point in an effort probability distribution.•The estimated point determines the type of estimate and how it should be evaluated.•Proper measures of estimation bias should give zero bias to perfect estimates of the point.•Presentation of proper estimation bias measures for different types of estimates.•Proof that a common measure of bias is not proper for any type of estimates. While prior software development effort estimation research has examined the properties of estimation error measures, there has not been much research on the properties of measures of estimation bias. Improved measurement of software development effort estimation bias. Analysis of the extent to which measures of estimation bias meet the criterion that perfect estimates should result in zero bias. Recommendations for measurement of estimation bias for estimates of the mean, median, and mode software development effort. The results include the recommendation to avoid a commonly used measure of effort estimation bias. Proper evaluation of estimation bias requires knowledge about the type of estimates evaluated, together with the selection of a measure of estimation bias that gives zero bias for perfect estimates of that type.