21 Criticism of the traditional PERT equations in Section 2.1 for estimating the means and standard deviations of activities has led to the development of alternative formulas by Perry and Greig (1975):

d N ij =

aij + 0.95mij + bij 2.95(14)

sN ij =

bij - aij 3.25(15)

where aij and bij are estimates for the 5 and 95 percentiles of the probability distribution of activity (i, j), and mij is the mode. Use these equations to recalculate and and answer the same questions as in Exercise 19. Compare the results.