The project evaluation and review technique is similar to the critical path method. The procedure to apply the process is almost the same as for CPM. Let’s first understand the basics of PERT before going into details.
- There are two major tools used for the analysis of the project. Critical Path Method (CPM) and Project Evaluation and Review Technique (PERT).
- There is a slight difference between CPM and PERT. The CPM uses a simple deterministic time estimate for calculation. On the other hand, PERT uses three different time estimates of the activity completion for the calculations.
In both techniques, a precedence network diagram is created based on the time estimates of the particular method. Later the forward and backward pass tools are applied to find out the earliest start and end and latest start and end times of the activities.
Moreover, the optimum route to the completion of the project is to evaluate along with the other critical findings in the form of critical activities, non-critical activities, and float of non-critical activities.
Time Estimations in PERT Analysis:
As explained earlier, a critical path method uses a single deterministic time estimate of activities for calculations. Whereas three times estimates are used in PERT analysis given as:
- Optimistic Time
- Most Likely Time
- Pessimistic Time
The expected time is calculated based on the above three estimates using the below formula:
The above expected time is used to make a visual precedence network diagram based on activities and dependencies.
Terms used in the Project Evaluation and Review Technique:
The project evaluation and review technique use different terms that are important to understand for the successful implementation of the technique.
Following are the essentials of PERT analysis:
- Work Breakdown Structure
- List of Activities
- Optimistic Time Estimate
- Most Likely Time Estimate
- Pessimistic Time Estimate
- Expected Time
- Dependencies of Activities
- Precedence Network Diagram
- Forward Pass
- Backward Pass
- Critical Path
- Critical Activities
- Non-Critical Activities
- Float or Slack
Steps to Apply Project Evaluation and Review Technique:
The project evaluation and review technique involve following specific terms:
- PERT Event
- PERT Predecessor Event
- PERT Successor Event
- PERT Activity
The project evaluation and review technique requires WBS, a list of activities, dependencies, and 3-time estimates for completion of activities.
After the availability of the above data. Meantime of each activity is calculated, and the precedence network diagram is constructed using nodes and arrows to represent project activities, their sequence, and mean durations.
Then, forward pass and backward pass methods are used to find the activities that have zero floats. These activities are marked as critical activities and a path is constructed by joining these activities.
All other activities that have some slack or float in the forward and backward pass scores can be delayed as per available margins without any direct impact on the project timeline.