摘要
本文讨论了PERT中作业持续时间的期望与方差的估计式的由来及适用范围。在假设作业持续时间服从正态分布或特定的β分布的条件下,导出了估计式及其适用范围;在假设作业持续时间的分布函数只知道三点值的条件下,借助逆变换关系及插值法,导出了期望与方差的表达式,进而归纳出估计式的适用范围。
This article discusses the Origin and the application range of the estimating formula for the expectation and the variance of activity time in PERT. It shows that if thc activity time has a normal distribution or a special beta distribution, the estimating formula and its application range can be derived, and if the values of only 3 points are known in the distribution function of activity time, the expression for the expectation and the variance can be derived with the help of the relation of inverse transformation and interpolation, and then the application range of formula can be deduced.
关键词
PERT
方差
正态分布
逆变换
统筹法
PERT, variance, normal distribution, inverse transformation, interpolation methods/activity time, expectation, beta distribution
