1. Monte Carlo vs. PERT Tutorial
Engineering 25
Monte Carlo vs. PERT Tutorial
Bruce Mayer, PE
Registered Electrical & Mechanical Engineer

2. NO Time Machines Allowed
In the Lecture on Monte Carlo Methods as used in the PERT Prob we allowed NEGATIVES in the Simulation
Someone might point out that no matter how hard we work we can not MAKE time
We can only USE time!
ReDo the simulation withOUT negative Times

3. Recall WhareHouse PERT chart
1. Project Start 2 3 4 5 6 7
1. Project End A B E F G H C D
The Schedule Elements
Excavate Foundation
Construct Foundation
Fabricate PreCast Components
Ship PreCast Parts to Building Site
Install PreCast Parts on Foundation
Build Roof
Finish Interior and Exterior
Inspect Result

4. Possibility of Negative Times
A Small MeanDuration:StdDev ratio indicates a higher probability of NEGATIVE durations
Task ID
Task Description
Mean Duration (days)
Std Dev (days) A
Foundation Excavation
3.5 1 B
Pour Foundation
2.5
0.5 C
Fab PreCast Elements 5 D
Ship PreCast Parts E
Tilt-Up PreCast Parts
1.5 F
Roofing 2 G
Finish Work 4
Expected Duration =
17 Days
Critical Path in Blue • Note in the circled cases the StdDev:Duration ratio is SMALL: 100%,, 50%, 30%

5. 5000-Trials Look for Negatives

6. Expected Standard Deviation (RMS)
Find the Expected Standard Deviation by GeoMetric (or Pythagorean or RMS) Calculation
In This case take the Std Dev from the GATING item A+B to find:

7. Compare Lack of Time Machine
Review and Run Files:
Monte_Carlo_Wharehouse_1604.m
Can MAKE time
Monte_Carlo_Wharehouse_Vectorized.m
NO Loops
Monte_Carlo_Wharehouse_No_Negatives.m
Can NOT make time
A “Flux Capacitor”