Variability in Individual Activities PERT accounts for uncertainty in activity times Uses 3 time estimates for each activity o Optimistic time (a) Pessimistic time (b) Most likely time (m) Calculations based on the Beta distribution Expected activity time t = (a + 4m + b)/6 Variance = [(b-a)/6]^2 Standard deviation = SQRT(variance) = (b -a)/6 Probability Density a m b 0 1 5 6 2 3 4 Time Required Beta Distribution Value: 3 For an activity, optimistic time (a) is 1, most likely time (m) is 4, and pessimistic time (b) is 7. Then, expected time will be standard deviation will be and variance will be Check Answer Variability in Individual Activities PERT accounts for uncertainty in activity times Uses 3 time estimates for each activity o Optimistic time (a) Pessimistic time (b) Most likely time (m) Calculations based on the Beta distribution Expected activity time t = (a + 4m + b)/6 Variance = [(b-a)/6]^2 Standard deviation = SQRT(variance) = (b -a)/6 Probability Density a m b 0 1 5 6 2 3 4 Time Required Beta Distribution Value: 3 For an activity, optimistic time (a) is 1, most likely time (m) is 4, and pessimistic time (b) is 7. Then, expected time will be standard deviation will be and variance will be Check