Difference between PERT And CPM

What is CPM?

CPM is an abbreviation for Critical Path Method. CPM is a project management technique developed in the late 1950s. It is helpful to plan, schedule, and controlling projects. The purpose of CPM is to analyze the time required to complete a project. With the help of CPM, users identify the critical path and calculate the earliest and latest start and finish times for each activity. CPM uses only a single time estimate for each activity.

CPM is commonly used in engineering, construction, and other industries to manage projects with well-defined activities and durations. It is helpful for projects with a high degree of certainty and where activities can be completed in a fixed sequence.

Difference between PERT and CPM

PERT (Program Evaluation and Review Technique) and CPM (Critical Path Method). Both are project management techniques. Both are used to plan, schedule and control projects. Both techniques may be used for similar purposes, but still, there are some differences between PERT and CPM. Let’s have a look at those differences:

Also read, Difference Between Data Analyst and Business Analyst

PERT Example

This ClickUp PERT chart example depicts the multi-step process of launching a website. Each arrow in this PERT chart is time-stamped by week to show when each job will occur in the project. It's important to remember that each circle represents a task but what we’re not seeing are all the subtasks and smaller steps involved in completing each larger item. This is a general snapshot of just the project milestones or key action items in traditional PERT chart fashion.

Advantages of PERT

Pert offers many advantages. Some of them are given below:

1. Project scheduling: Pert provides better project scheduling. Pert provides a detailed analysis of project activities, their expected durations, and their dependencies, allowing project managers to create a more accurate and reliable project schedule.
    
2. Risk management: Pert provides better risk management. Pert considers the uncertainty and risk associated with project activities using three-time estimates for each activity. This allows project managers to identify potential risks and take steps to mitigate them.
    
3. Improved communication: Pert uses a network diagram to visually represent project activities and their interdependencies, making it easier for project managers to communicate project details and status to team members, stakeholders, and clients.
    
4. Resource allocation: Pert provides a detailed understanding of each project activity's time and resource requirements, allowing project managers to allocate resources more efficiently and effectively.
    
5. Improved project control: Pert provides a mechanism for tracking project progress against the planned schedule, allowing project managers to identify potential delays or deviations and take corrective action as necessary.

Disadvantages of PERT

Some of the Pert disadvantages are the following:

1. Time-consuming: Pert requires significant time and effort to develop a detailed network diagram, estimate activity durations, and calculate the critical path. This can be a disadvantage for projects with tight deadlines or limited resources.
    
2. Complex: Pert is a complex project management technique that requires a good understanding of project scheduling and network analysis. This can be a disadvantage for project managers unfamiliar with the method or projects with inexperienced project teams.
    
3. Costly: Developing a Pert network diagram and estimating activity durations can be expensive, especially for large and complex projects. This can be a disadvantage for projects with limited budgets or cost constraints.
    
4. Uncertainty: Pert relies on probabilistic time estimates, which are subject to a degree of uncertainty. This can be a disadvantage for projects with high uncertainty or risk, as it can be difficult to accurately estimate activity durations and calculate the critical path.
    
5. Lack of flexibility: Pert assumes that activities must be completed in a specific sequence and that there is no flexibility to change the order of activities. This can be a disadvantage for projects that require flexibility or agility to adapt to changing project requirements or unexpected events.

CPM Example

The path with the longest duration in the diagram above is Start-D-E-F-G-End, which is also the critical path with a length of 17. The other two non-critical paths are Start-A-B-C-G-End, which has a duration of 10 and hence a slack or float of 7, and Start-D-H-I-End, which has a duration of 11 and a float of 6 days.

Once the critical path has been established, the team can investigate whether the duration of the critical path can be reduced if necessary. Crashing (putting extra resources on the critical path) and fast-tracking (performing activities in parallel) techniques are used. Compressing the critical path shortens the overall project length, allowing it to meet the deadline.

Advantages of CPM

There are many advantages to using CPM. Here are some of the key benefits given below:

1. Identifies critical path: With the help of CPM, users can identify the critical path. This allows users to focus on important activities and allocate resources accordingly.
    
2. Project scheduling: CPM helps users to develop a project schedule. Project scheduling is possible by estimating the time required to complete each activity and identifying the times for each activity.
    
3. Provides clear project overview: CPM gives a clear overview of the project activities, their dependencies, and their durations. This helps project managers to understand the project scope, identify potential problems, and develop contingency plans.
    
4. Optimizes resource allocation: CPM helps project managers optimize resource allocation by identifying activities that can be completed concurrently and those that must be completed in sequence. This helps to minimize project duration and resource requirements.
    
5. Improves communication: CPM helps project managers communicate project requirements and progress to stakeholders, including team members, sponsors, and customers. This improves collaboration and reduces the risk of misunderstandings or delays.

Disadvantages of CPM

CPM (Critical Path Method) offers many advantages. Some of them are given below:

1. Well-defined activities: CPM assumes that activities are well-defined. This can be a disadvantage for complex projects where estimating activity durations may be difficult.
    
2. Ignore resource constraints: CPM does not take into account resource constraints. This can be a disadvantage for projects where resource availability is a critical factor in project success.
    
3. Ignore non-critical activities: CPM focuses only on the critical path. This can be a disadvantage for projects where non-critical activities are also important for project success.
    
4. Does not consider project risk: CPM does not take into account project risk or uncertainty, which can be a disadvantage for projects with a high degree of uncertainty or where unexpected events may occur.
    
5. Requires detailed planning: CPM requires a detailed project plan with well-defined activities and durations. This can be a disadvantage for projects with limited resources or where project requirements are still being defined.

Frequently Asked Questions

What is the main difference between CPM and PERT?

PERT is a project management method that incorporates both the planning and organizing phases, as well as the scheduling and control strategy, whereas CPM is a statistical project management process that focuses solely on the scheduling and control parts.

What is the formula for PERT?

The Expected Time (TE) in PERT is calculated using the following formula:

TE = (TO + 4 * TM + TP) / 6
Where TO is the Optimistic time estimate, TM is most likely the time estimate, and TP Pessimistic time estimate

Why PERT is considered to be more exact and precise than CPM?

Due to its emphasis on unpredictable activity durations and incorporation of probabilistic analysis, PERT (Program Evaluation and Review Technique) is believed to be more accurate than CPM (Critical Path Method), offering a better representation of project timetable variability.

Conclusion

We hope this article helped you understand the difference between Pert and CPM. We have also discussed the Introduction, advantages, and disadvantages of Pert and CPM. You will find straightforward explanations of almost every topic on this platform. You can read more such articles on our platform, Code360. So take your learning to the next level using Coding Ninjas.