Programme Evaluation & Review Technique

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Analysis with the Help of PERT and CPM

Program Evaluation and Review Technique (PERT) and Critical Path Method

 (CPM) are essential tools in project management, used for planning, scheduling, and controlling complex projects. Here’s an in-depth and concise explanation of these techniques:

Program Evaluation and Review Technique (PERT)

PERT is a project management technique designed to analyze and represent the tasks involved in completing a project. It focuses on the time required to complete each task and the dependencies between tasks.

Key Concepts:

  • Time Estimates:
    • Optimistic Time (O): The minimum possible time required to complete an activity, assuming everything proceeds better than expected.
    • Pessimistic Time (P): The maximum possible time required to complete an activity, assuming everything goes wrong but excluding major catastrophes.
    • Most Likely Time (M): The best estimate of the time required to complete an activity, assuming normal conditions.
  • PERT Formula: The expected time (TE) for an activity is calculated using the formula:
  • TE = O+4M+P6​
  • This formula provides a weighted average of the three time estimates, accounting for uncertainty in activity durations.

Steps in PERT Analysis:

  • Define the Project: Break down the project into distinct tasks or activities.
  • Identify Dependencies: Determine the sequence of tasks and their dependencies.
  • Estimate Times: Obtain optimistic, pessimistic, and most likely time estimates for each task.
  • Calculate Expected Times: Use the PERT formula to calculate the expected time for each task.
  • Construct Network Diagram: Create a visual representation of the tasks and their dependencies.
  • Identify Critical Path: Determine the longest path through the network that dictates the project's minimum duration.
  • Monitor Progress: Update the network diagram and time estimates as the project progresses.

Example: For a task with:

  • Optimistic Time (O) = 2 weeks
  • Most Likely Time (M) = 4 weeks
  • Pessimistic Time (P) = 6 weeks

The expected time (TE) would be:

TE = 2+4×4+66 = 4 weeks

Critical Path Method (CPM)

CPM is a project management technique that focuses on identifying the longest path of dependent activities and calculating the minimum time required to complete a project. It helps in managing project schedules and ensuring timely completion.

Key Concepts:

  • Critical Path:
    • The longest sequence of activities that determines the shortest time in which a project can be completed. Any delay in the critical path directly impacts the project’s overall duration.
  • Total Float (Slack):
    • The amount of time that a task can be delayed without affecting the project’s end date. Tasks on the critical path have zero float.

Steps in CPM Analysis:

  • List Activities: Identify all tasks required to complete the project.
  • Determine Sequence: Establish the order and dependencies of activities.
  • Draw Network Diagram: Create a flowchart that visually represents activities and their dependencies.
  • Estimate Durations: Determine the duration for each activity.
  • Calculate Critical Path: Identify the longest path through the network diagram by summing the durations of tasks on each path.
  • Update Network: Adjust the network diagram and critical path as the project progresses.

Example: For a project with tasks A, B, C, and D:

  • A: Duration = 3 weeks
  • B: Duration = 4 weeks (depends on A)
  • C: Duration = 2 weeks (depends on A)
  • D: Duration = 5 weeks (depends on B and C)

The critical path could be:

  • Path 1: A → B → D = 3 + 4 + 5 = 12 weeks
  • Path 2: A → C → D = 3 + 2 + 5 = 10 weeks

The critical path is A → B → D, with a duration of 12 weeks.

Benefits of PERT and CPM:

  • Improved Planning: Provides a structured approach to project planning, helping to identify task dependencies and timelines.
  • Time Management: Assists in estimating project durations more accurately and managing schedules effectively.
  • Resource Allocation: Helps in optimizing the allocation of resources by highlighting critical tasks.
  • Risk Management: Identifies critical tasks and potential delays, aiding in risk management and mitigation.
  • Enhanced Communication: Visual representations of tasks and dependencies improve communication among stakeholders.

Conclusion

PERT and CPM are powerful techniques for project management that offer a structured way to plan, schedule, and control projects. While PERT focuses on estimating the time required for tasks and dealing with uncertainties, CPM emphasizes identifying the critical path and managing project timelines. Using these methods together provides a comprehensive approach to managing complex projects and ensuring timely completion.