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?

  1. Critical Path Method (CPM)
  2. Program Evaluation and Review Technique (PERT)
  3. Monte Carlo simulation
  4. 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.

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