A contractor's project being analyzed by PERT has an estimated time for the critical path of 120 days. The sum of all activity variances is 81; the sum of variances along the critical path is 64. The probability that the project will take 130 or more days to complete is
A) 0.1057
B) 0.1335
C) 0.8512
D) 0.8943
E) 1.29

Question

Quizplus · Accepted Answer

The standard deviation of the critical path is the square root of the sum of variances along the critical path, which is √64 = 8. The Z-score for 130 days is (130 - 120) / 8 = 1.25. Using the standard normal distribution table, the probability of Z being less than 1.25 is approximately 0.8943. Therefore, the probability of the project taking 130 or more days is 1 - 0.8943 = 0.1057.

A Contractor's Project Being Analyzed by PERT Has an Estimated