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CPM and PERT and their uses

Short answer

CPM uses deterministic time estimates to find the critical path, project duration and floats, and supports time-cost trade-off, suitable for construction projects with known durations. PERT uses three probabilistic time estimates (optimistic, most likely, pessimistic) to find expected duration and probability of completion, suitable for research and development projects with uncertain times.

Explain CPM and PERT and their uses.

CPM (Critical Path Method)

CPM was developed in 1957 by Du Pont and Remington Rand for plant maintenance and construction. It is a network technique with deterministic (single) time estimates for each activity. It finds the critical path, project duration and floats, and links time with cost (cost-time trade-off).

PERT (Programme Evaluation and Review Technique)

PERT was developed in 1958 by the US Navy for the Polaris missile project. It is probabilistic: three time estimates are used - optimistic tot_o, most likely tmt_m and pessimistic tpt_p.

te=to+4tm+tp6,σ=tp−to6t_e = \frac{t_o + 4t_m + t_p}{6}, \qquad \sigma = \frac{t_p - t_o}{6}

It is event oriented and gives the probability of finishing by a given date.

Uses

CPMPERT
Construction projects (roads, buildings, bridges) with known durationsResearch, development and new, first-time projects
Finding critical path and floatsEstimating the chance of meeting a deadline
Time-cost trade-off and crashingProjects where time estimates are uncertain
Resource levelling and schedulingPlanning and review of big programmes such as defence and hydropower tunnelling
Monitoring and updating the scheduleControl of time (cost is not the main concern)

Both help to plan, schedule and control large projects, show inter-dependence of activities, and focus management attention on critical activities.

✓ Answer checked by Claude Opus 5.5 (high effort)

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