We indicated in Example 15.5 that the mean project length from the simulation is greater than the project length of 62 days from substituting the mean activity durations (the ones used in earlier...

We indicated in Example 15.5 that the mean project length from the simulation is greater than the project length of 62 days from substituting the mean activity durations (the ones used in earlier sections). Note that the PERT distributions we used in the example, with the exception of activity D, are either symmetric around the most likely value or skewed to the right.

Could this skewness to the right lead to the rather large mean project length from the simulation? Experiment with the parameters of the PERT distributions in the example, always keeping the same mean durations. For example, you could change the parameters of activity A from 8, 9, 16 to 7, 10, 13 (to make it symmetric) or to 4, 11, 12 (to make it skewed to the left). Each of these has the same mean, 10, and there are many other combinations that have mean 10 that you could try. Run the simulation with a few such combinations. What effect does it have on the mean project length from the simulation? Does the mean project length continue to be greater than 62? What effect does it have on the percentiles of the simulation, such as the 5th or 95th percentiles? Do you conclude that the shapes of the input distributions, given that they keep the same means, have much effect on the distribution of project length?

Example 15.5