Week 4 Project

Project Scheduling Techniques

Project scheduling techniques continue to be developed today. Consider how some types of projects just never seem to be completed on time, and they get delayed time

and again to everyone's frustration. Despite schedule constraints often being the hardest to deal with in any given project, delays seem rampant in some �elds.

Before discussing project scheduling techniques, let's visit the idea of an activity. While discussing the work breakdown structure (WBS) in Week 3, you would have

noted the WBS represents the project scope in the form of a hierarchy of the project deliverables. A WBS is further elaborated by the speci�cation of the activities to produce the deliverables.

Do not confuse an activity with a deliverable. As simple as it sounds, one way to keep the idea of an activity clear from the idea of a deliverable is that activities are

expressed with action verbs like "Build . . .," "Write . . .," or "Produce . . .," whereas deliverables are not. Deliverables are outputs, not actions.

Once the activities needed to accomplish all WBS deliverables are de�ned, they can be scheduled by putting them all together in their logical, complex sequences,

according to how they are sequentially dependent.

Two project scheduling techniques are critical path method (CPM) and program evaluation and review technique (PERT). Though the CPM is a deterministic technique and PERT is a probabilistic technique, both have almost become one, as they share similarities. They both assume that a small activity which makes the longest path

control the entire project. However, your assignments focus more on deterministic activity estimates and CPM. Though the terms PERT and CPM are often used

interchangeably, it is important for you to have complete clarity about them.

CPM is a deterministic technique. For any given activity, it assumes only one estimate of time with no estimated variation around it. Therefore, the overall length of any

activity, path, or project can be easily determined through some simple math – though doing a “backward pass” and a “forward pass” may get tedious. The CPM is a pure

scheduling technique, and its purpose is to build a project schedule based on deterministic estimates of each activity’s time.

PERT is a probabilistic technique. It uses the laws of probability and three different estimates of a project’s duration – an optimistic estimate, a most likely estimate, and a pessimistic estimate. Getting these estimates can be fraught with human frailty, but when the data is put together, project schedules can be evaluated in accordance with

the likelihood of success or failure. Therefore, PERT is a pure risk management technique, as risk deals with probabilities of failure.