1. Critical Path Method (CPM)

CPM is a deterministic scheduling technique that identifies the longest path of dependent activities through the project, determining the shortest possible completion time.

Steps in CPM:

• List project activities.
• Identify dependencies (which task follows which).
• Estimate activity durations.
• Draw a network diagram.
• Compute the earliest and latest start/finish times.
• Identify the Critical Path (activities with zero float).

Key Terms:

• Float (Slack): Time by which an activity can be delayed without affecting project completion.
• Critical Path: Sequence of tasks that determines project duration.
• Crash Duration: Minimum time by increasing resources.

Example:

If the critical path is A–C–E–G = 120 days, any delay in these activities delays the project itself.

“Managing the critical path means managing the project’s heartbeat.”

2. Program Evaluation and Review Technique (PERT)

PERT is a probabilistic model used when activity durations are uncertain.
It estimates the expected time using three scenarios:

TE = (O + 4M + P) / 6

Where:

• O = Optimistic time
• M = Most likely time
• P = Pessimistic time

Example:

For an activity with O = 4, M = 6, P = 10 days:

TE = (4 + 4×6 + 10) / 6 = 6.33 days

When to Use:

• R&D or design-heavy projects.
• Early-stage planning where data is limited.
• Risk-based scheduling in EPC projects.

Comparison:

When to Use:

• R&D or design-heavy projects.
• Early-stage planning where data is limited.
• Risk-based scheduling in EPC projects.

Comparison: