Critical Path Method (CPM)
A scheduling technique that calculates the shortest possible project duration and measures the amount of float on each logical path in the schedule network.
Key Points
- Identifies the critical path: the longest path through the network with zero total float; any delay on it delays the project finish.
- Uses forward and backward pass to compute early/late start and finish dates and total float for activities and paths.
- The critical path can shift during execution, and there can be multiple critical paths in some schedules.
- Informs schedule compression choices (crashing, fast tracking) and highlights where schedule flexibility exists.
Example
A project schedule lists activities with durations and dependencies. The team draws the network diagram and runs forward and backward passes to find early/late dates. The path A-B-D-E totals 40 days with zero float, while path A-C-E totals 35 days with 5 days of float. To finish sooner, the manager considers crashing activities on A-B-D-E since only shortening the critical path reduces the overall project duration.
PMP Example Question
Which technique determines the minimum project duration and identifies where schedule float exists across network paths?
- Critical Path Method (CPM)
- Program Evaluation and Review Technique (PERT)
- Monte Carlo simulation
- Resource leveling
Correct Answer: A — Critical Path Method (CPM)
Explanation: CPM calculates early and late dates, total float, and the longest path, revealing the minimum project duration and schedule flexibility.