What’s the Difference between PERT and CPM?

PERT and CPM are two forms of Network Chart that are represented differently, and take different approaches to calculating schedules. For both, the roots lie in the 1940s and the way the Manhattan Project was planned.

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Comparing PERT and CPM

My intention is not to give you a detailed explanation of either PERT or the CPM. Rather, to simply highlight the main differences between them.

Program Evaluation and Review Technique

• 1950s
• Originally developed by the US Navy and Booz Allen Hamilton
• Activities on Lines – nodes connect tasks. The focus is on activities.
• 3-point estimates for each duration – Most Likely, pessimistic (longest plausible) and optimistic (quickest plausible) estimates – not symmetric – weighted average: (O + 4L + P)/6.
• Hence PERT is a probabilistic approach.
• This makes PERT more suitable for projects that are more novel.
• PERT was designed to optimize and control schedule only, by understanding the spread of possible schedule outcomes for each activity.
• Popular in the R&D sector

Critical Path Method

• 1950s (a little later than PERT)
• Originally developed by Du Pont and Remington Rand
• Activities on Nodes (boxes) with Arrows as linkages between them. The focus is on events.
• Single-point estimates for activity durations are better when activities are more clearly defined.
  
  Hence CPM is a deterministic approach.
• This makes CPM more suitable for projects that are more repetitive.
• CPM is used to control schedule and budget, and helps calculate the trade-offs between them, using an understanding of float and critical or non-critical activities
• Popular in the construction sector

Recommended Videos and Articles to Help with PERT & CPM, and other aspects of Project Planning

Carefully curated article and video recommendations for you:

• What is a PERT Chart? | Video
• Make Your Project Estimation More Reliable, Using the PERT Method
• What is CPM (Critical Path Method)? | Video
• Beyond Gantt Charts: How to Boost your Project with the Critical Chain Method
• Project Planning Process: Navigate the Many Steps You Need
• Project Planning Process – How to Build Effective Project Plans | Video
• 12 Project Planning Mistakes… and How to Fix Them
• Capabilities Based Planning: A Primer
• Planning Performance Domain: How to Plan a Solution to Meet Your Goals

What Kit does a Project Manager Need?

I asked Project Managers in a couple of forums what material things you need to have, to do your job as a Project Manager. They responded magnificently. I compiled their answers into a Kit list. I added my own. 

Check out the Kit a Project Manager needs

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