CPM and PERT Notes

Critical Path Method (CPM)

• CPM identifies necessary project tasks and determines scheduling flexibility.

• It revolves around discovering the most important tasks, identifying dependencies, and calculating durations.

Why use CPM?

• Improves future planning by comparing expectations with actual progress.

• Facilitates effective resource management by prioritizing tasks.

• Helps avoid bottlenecks by plotting project dependencies.

Finding the critical path

1. List project tasks.

2. Identify task dependencies.

3. Create a network diagram.

4. Estimate task duration.

5. Find the critical path (longest sequence).

6. Calculate the total float.

List Activities

• Use a Work Breakdown Structure.

Identify Dependencies

• Determine dependent tasks.

• Identify parallel work.

Create a Network Diagram

• Flowchart of activity chronology.

• Use boxes for tasks and arrows for dependencies.

Estimate Task Duration

• Estimate duration based on experience, previous data, or industry standards.

• Forward pass: calculates early start (ES) and early finish (EF) dates.

  • ES is the highest EF from predecessors.

  • EF is ES + duration.

• Backward pass: calculates late start (LS) and late finish (LF) dates.

  • LS is LF - duration.

  • LF is the lowest LS from successors.

Calculate the Float

• Float (slack) is task flexibility.

• Indicates delay potential without affecting the project end date.

• Critical tasks have zero float.

• Positive float tasks are non-critical.

Calculate the Critical Path

• Write down start and end times for each activity.

• Determine the total sequence duration.

• The longest duration sequence is the critical path.

CPM - Advantages

• Provides correct completion date and activity float.

• Encourages planning, resource allocation, and monitoring.

• Improves efficiency, productivity, and deadline likelihood.

• Offers visual representation and known completion times.

CPM - Disadvantages

• Doesn't handle personnel or resource allocation.

• Not suitable for very large, complex projects.

Project Evaluation and Review Technique (PERT)

• PERT is used to schedule, organize, and map out project tasks with visual representation.

• Creates a roadmap for scheduling, communicating objectives, mapping projects, and estimating task times.

The 5 steps of creating a PERT chart

1. Identify project tasks.

2. Define task dependencies.

3. Connect project tasks.

4. Estimate project timeframe.

5. Manage task progress.

Identify Project Tasks

• Identify necessary tasks through business cases, communication plans, or kickoff meetings.

Define Task Dependencies

• Task dependency: a task reliant on another's completion.

• Dependencies help track work and ensure completion using visualization.

Connect Project Tasks

• Use arrows (tasks) and nodes (events/milestones).

Estimate Project Time Frame

• Estimate overall timeframe using CPM and the PERT formula.

• Time estimates: optimistic, pessimistic, most likely.

PERT Formula

$O + (4 \times M) + P) \div 6$

• Example: $(30 min + (4 \times 45 min) + 60 min) \div 6 = 45$ minutes

Managing Task Progress

• Manage dependencies and mitigate issues, updating as needed.

PERT Chart Creation

• Draw numbered nodes (parent tasks).

• Connect nodes with arrows for task dependencies.