A Pitfall of estimated software cost

A pitfall hidden in the software cost estimation process is presented. Software project cost estimation process based on the quantile estimation software project cost distribution is not sub-additive and produce unrealistic cost estimates. Sub-additive is the process where the estimation of parts is less than or equal to the estimation of the whole. Further a solution is presented and illustrated how sub-additivity could be achieved by dealing with the expectation of the probability distribution beyond a given quantile.