Expected Delays in Completing Projects under Uncertainty

A method is proposed to estimate, rationally, a contingency covering probable delays in completing projects. Projectcompletion time is assumed random variable distributed normally with given expected value and variance. Two purestrategies and a mixed strategy for decreasing expected delay, if it turns out to be unacceptable, are presented. A new functionSDF(ZC), as a function of a standard normal variable ZC corresponding to contract time TC, is derived and given also in atable form for calculation simplicity. The mixed strategy of compressing both expected project completion time and itsvariance, to achieve a desirable level of expected project delay, leads to a nonlinear program and solved by Solver/Excel