PERT and CPM are tools used in Project Management. They are network analysis tools. PERT gives us an understanding of how the project is functioning with reference to the earliest possible dates of activities and the latest possible dates of activities.
So, if one activity takes 10 days and a second takes 5 days, and if both these activities can run in parallel, the second activity can start at the earliest on the 1st day or latest on the 6th day. PERT technique involves this kind of an analysis.
In the CPM, the longest path of the project is identified. This path, when delayed, actually delays the whole project.
Most project managers either lean towards PERT or CPM. Most executives are, however, used to just CPM. The problem with CPM is that, it often results in resource allocation on an activity at the cost of other activities... Hence, the other activities start developing delays and ultimately, the whole project gets delayed.
While most project management books refer to PERT and CPM in depth, one must exercise caution on the same. Current trends in management involve using these tools as deterministic models. This means that an activity requires 10 days and 10 days only... However, we all know that real-life problems are usually probabilistic. In the PERT example, a model is fitted into the system. However, its often hard to implement this. I am currently the Lead for the Program Planning for a Greenfield project. It has around 100000 activities divided . By Feb 09, we are expecting 400 000 activities. Such large programs are split into projects. Ours is split into 240 projects. So, CPM is a good tool for us, but PERT is used on a selective basis.
If you are using that for a run-of-the-mill project management exercise like a construction project, PERT and CPM are probably good options. For R&D Projects, you might consider going for GERT, a technique that supports probabilistic loops in the project plan. If you are going for a software implementation project like SAP or something, with reputed vendors you would need to use a tool called the 'waterfall model' which essentially supports PERT and CPM.
However, do understand that its better to go for a 'management by milestones' approach if you have a lot of uncertainty in the scope of the project. Once the major milestones are fixed, it might make sense to work the project out using network techniques to detail out the plan. One could use PERT and CPM at that stage.
5th November 2008 From United States