Project network techniques

11/July/2025 01:43 Share:

? Network Analysis, CPM & PERT

? Network Analysis – Meaning

Network Analysis is a project management technique used to plan, schedule, monitor, and control complex projects. It involves breaking down a project into activities and arranging them in a logical sequence using a network diagram. This helps identify the relationship between tasks, estimate durations, allocate resources, and highlight dependencies. Tools such as Critical Path Method (CPM) and Program Evaluation and Review Technique (PERT) are widely used under this method to optimize project timelines and avoid delays.

? Critical Path Method (CPM)

CPM is a deterministic technique used in project planning to identify the longest path through the project, known as the critical path. This path determines the shortest time in which a project can be completed. Any delay in a critical activity directly affects the project duration. CPM is most useful when activity durations are known and constant.

Each task or activity is assigned a fixed duration, and the project network is analyzed to determine:

The earliest start (ES) and earliest finish (EF)
The latest start (LS) and latest finish (LF)
The total float (slack time), i.e., how much delay is allowed without affecting the project

Example: If Task A takes 3 days, Task B takes 4 days, and Task C takes 2 days and depends on A and B, the critical path is A → B → C = 3 + 4 + 2 = 9 days. Any delay in this chain delays the whole project.

? PERT – Program Evaluation and Review Technique

PERT is a probabilistic project scheduling tool that considers uncertainty in activity durations. It is mainly used for research, development, and projects where exact time estimates are difficult. PERT uses three time estimates for each activity:

Optimistic Time (O): Minimum possible time if everything goes right
Most Likely Time (M): Best estimate of normal time
Pessimistic Time (P): Maximum possible time if things go wrong

PERT Expected Time Formula:

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

Example:
For an activity with O = 2 days, M = 4 days, P = 8 days:
TE = (2 + 4×4 + 8) / 6 = (2 + 16 + 8) / 6 = 26 / 6 ≈ 4.33 days

PERT also helps calculate the standard deviation and variance of each activity to estimate project completion probability and risk:

Standard Deviation (σ): (P - O) / 6
Variance: [(P - O) / 6]²

? Comparison: CPM vs PERT

CPM is used for projects with predictable durations; PERT is used for uncertain estimates.
CPM uses a single time estimate per activity, while PERT uses three.
CPM focuses on time-cost trade-offs; PERT focuses on time-risk analysis.

✅ Conclusion

Both CPM and PERT are vital tools in project management. While CPM is suitable for construction, production, and routine projects, PERT is ideal for research and development or innovation-based tasks. Network analysis as a whole improves scheduling accuracy, highlights dependencies, and helps project managers make informed decisions to meet deadlines effectively.