Programme Evaluation Review Technique (PERT)

PERT

Description also available in video format (attached below), for better experience use your desktop.

Introduction

• PERT is a project management tool used to schedule, organize, and coordinate tasks within a project.
• Developed in the 1950s by the U.S. Navy for the Polaris missile program.
• It is particularly useful for projects where time is the critical factor and activity durations are uncertain.

Objectives 

1. Plan and control large projects effectively.
2. Identify the critical path to know which tasks affect project duration.
3. Estimate minimum time needed to complete a project.
4. Monitor project progress and update timelines dynamically.

Key Concepts

Term	Meaning
Activity	Task/job that consumes time and resources
Event (Node)	Milestone marking the start or end of activities
Network	Diagram representing sequence and dependencies of activities
Slack/Float	Amount of time an activity can be delayed without delaying the project
Critical Path	Longest duration path through the network
Critical Activities	Activities with zero slack – any delay here delays the entire project

Time Estimation

Each activity has three time estimates

Estimate Type	Symbol	Description
Optimistic Time	(O)	Minimum possible time required, assuming everything goes well
Most Likely Time	(M)	Best estimate under normal conditions
Pessimistic Time	(P)	Maximum time required, assuming worst-case scenario

🧮 Expected Time (TE)

    TE=(O+4M+P) /6

Steps 

1. Identify the project and activities involved.
2. Determine sequence and dependencies among activities.
3. Draw the network diagram.
4. Estimate time using the O, M, P for each activity.
5. Calculate TE and variance for each activity.
6. Find the Critical Path – the sequence with the longest time (TE).
7. Update and monitor progress regularly.

Critical Path Method (CPM) vs PERT

Aspect	PERT	CPM
Time Estimates	Probabilistic (O, M, P)	Deterministic (fixed time)
Focus	Time	Time and cost
Suitable For	R&D, new/complex projects	Construction, manufacturing
Flexibility	High uncertainty	Low uncertainty

Advantages 

• Handles uncertainty in project scheduling.
• Provides realistic time estimates.
• Identifies critical activities for better monitoring.
• Aids in effective resource allocation.
• Useful for large and complex projects.

Limitations 

• Can be time-consuming and complex for large networks.
• Assumes independence between activities.
• Less effective when time estimates are highly subjective.
• No focus on cost; time-centric only.

Applications 

• Hospital planning & equipment procurement
• Healthcare facility construction projects
• Software development
• R&D projects
• Defense and aerospace projects

Video Description

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