Project Planning & Scheduling

CPM & PERT CPM – Critical Path Method (no statistical basis incorporated) PERT – Program Evaluation & Review Technique (statistical basis incorporated) → activity: work component needed to be accomplished (a task with definite beginning and ending points) O event: node designating beginning and/or ending activities

PERT network activity times te: expected time of an activity σe: standard deviation of activity time (σe)2: variance of activity time to = optimistic time (1 in a 100 chance less) tm = most likely time tp = pessimistic time (1 in a 100 chance more)

Determining PERT network activity times

PERT procedure Construct PERT network May need to insert dummy activity(ies) for diagram completion Dummy activity is a fictitious activity with no actual time Determine at each node TE, TL, and TS TE = earliest expected time TL = latest allowable time Ts = slack time (difference between TE and TL, freedom available in deciding when to start an activity without jeopardizing overall timely completion)

The critical path Evaluate all paths through the network – path where total activity times are the most of any path is the critical path Variance along the critical path is equal to the sum of the variances of each activity along the critical path

A PERT example

Another PERT example

Creating the PERT network