7.2: PERT Analysis
Check Your Knowledge
Questions: PERT
1. PERT uses three time estimates. What are they?
2. How is Te calculated?
3. What does a PERT analysis determine?
PERT Exercise: Tutorial
The goal of this exercise is to learn how to estimate the probability of a project being completed within a certain duration.
Download this spreadsheet, and then watch this instructional video on PERT Probability Analysis that will walk you through an analysis of the following network:
| ID | Description | a | m | b | Te | Predecessor |
| A | External Specs | 6 | 8 | 12 | None | |
| B | Review Design Features | 2 | 2 | 5 | A | |
| C | Document New Features | 2 | 3 | 5 | A | |
| D | Write Software | 50 | 60 | 90 | A | |
| E | Program and Test | 50 | 60 | 90 | B | |
| F | Edit and Publish Notes | 2 | 2 | 4 | C | |
| G | Review Manual | 2 | 2 | 4 | C | |
| H | Alpha Site | 16 | 20 | 30 | E, F | |
| I | Print Manual | 9 | 10 | 15 | G | |
| J | Beta Site | 7 | 10 | 18 | H, I | |
| K | Manufacture | 8 | 12 | 20 | J | |
| L | Release and Ship | 2 | 3 | 5 | K |
For Your Reference
The following steps will be used in this exercise to conduct a PERT Analysis:
- Calculate Te duration values for each task in an excel spreadsheet.
- Enter Te duration values into MS Project or other project management information system and determine critical path. Note: One could also create a network diagram to determine the critical path.
- Enter the values for the tasks on the critical path into the PERT calculator spreadsheet in order to determine estimate variances.
- Estimate probabilities that our project will complete within a given time period.
Exercise: PERT Analysis
Conduct a PERT Analysis on the following project and answer the questions below.
| ID | Description | O | M | P | Te | Predecessor |
| A | Survey | 4 | 5 | 7 | None | |
| B | Soils Report | 17 | 20 | 25 | A | |
| C | Traffic Design | 25 | 30 | 40 | A | |
| D | Lot Layout | 5 | 5 | 7 | A | |
| E | Approve Design | 75 | 80 | 90 | B, C, D | |
| F | Illumination | 12 | 15 | 15 | E | |
| G | Drainage | 20 | 30 | 45 | E | |
| H | Landscape | 20 | 25 | 50 | E | |
| I | Signing | 18 | 20 | 22 | E | |
| J | Bid Proposal | 8 | 10 | 12 | F, G, H, I |
1. What is the project duration based on Te?
2. What is the chance that the project will be completed in the duration of our current critical path?
3. What time should the project manager estimate if they want to be 95% sure that the project will be completed within that time period?
4. What is the buffer time that should be added to a project’s critical tasks in order to be 95% sure that the project completes on time?
