Page 64 - The Six Sigma Project Planner

The most prominent of these procedures have been PERT (Program Evaluation and
Review Technique) and CPM (Critical Path Method). The two approaches are usually
referred to as PERT-type project management systems. The most important difference
between PERT and CPM is that originally the time estimates for the activities were
assumed to be deterministic in CPM and were probabilistic in PERT. Today, PERT and
CPM actually constitute one technique and the differences are mainly historical.
Modern project management tends more toward CPM than PERT.
CPM systems are used to:
• aid in planning and controlling projects
• determine the feasibility of meeting specified deadlines

• identify the most likely bottlenecks in a project
• evaluate the effects of changes in the project requirements or schedule

• evaluate the effects of deviating from schedule
• evaluate the effect of diverting resources from the project or redirecting additional
resources to the project.
Project scheduling by CPM consists of four basic phases: planning, scheduling,
improvement, and controlling.
The planning phase involves breaking the project into distinct activities. The time
estimates for these activities are then determined and a network (or arrow) diagram is
constructed, with each activity being represented by an arrow.

The ultimate objective of the scheduling phase is to construct a time chart showing the
start and finish times for each activity as well as its relationship to other activities in the
project. The schedule must identify activities that are critical in the sense that they must
be completed on time to keep the project on schedule.
It is vital not to merely accept the schedule as a given. The information obtained in
preparing the schedule can be used to improve it. Activities that the analysis indicates
to be critical are candidates for improvement. Pareto analysis can be used to identify
those critical elements that are most likely to lead to significant improvement in overall
project completion time. Cost data can be used to supplement the time data. The
combined time/cost information can be analyzed using Pareto analysis.
The final phase in CPM project management is project control. This includes the use of
the network diagram and time chart for making periodic progress assessments. CPM
network diagrams can be created by a computer program or constructed manually. (For
details, see Appendix, p. 199.)

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