Time Estimates for Individual Activities:
A) Weighted Average Activity Time, t = (a + 4m + b)/6
B) Standard deviation of activity times, σt = (b-a)/6
C) Standard deviation of project completion, σT= √ (∑ σt2)
a = optimistic completion time (1 in 100 chance of completing the activity earlier under normal conditions)
m = most likely activity time
b = pessimistic completion time (1 in 100 chance of completing the activity later under normal conditions)
t = weighted average activity time
σt = standard deviation of activity completion
σT = standard deviation of project completion