**6.6 Monte Carlo simulation**

This method will create a project duration that is closer to reality than CPM or PERT. This method uses computers to simulate the outcome of a project based on PERT estimates and the network diagram, but does not use the PERT formula. Simulation can tell you the probability of completing the project on any specific day, probability of completing the project for any specific amount of cost, probability of any task actually being on the critical path, and overall project risk.

The network diagram shows the sequence of work elements required to reach project completion. Note that the initial stage of the network diagramming does not require time or cost estimates. We simply determine the most logical and technically viable approach to completing the project and use the network format to visualize this scenario. You must remember that initial network diagram logic is dictated by work-related constraints only; you should not introduce resource and time constraints at that time.

Once the network illustrating a logical flow of work elements in the project is developed, you can assign (or assume) resources to each activity and develop initial task time estimates. These estimates are then aggregated across the network to calculate its critical path, and the slack times associated with each activity. These calculations are based on a forward pass to compute the earliest start and finish times for each activity, and then a backward pass to determine the latest start and finish times of the activity. Then the difference between the earliest and latest times for any activity gives us its slack time. All activities with slack times of zero duration constitute the critical path(s) for the project.
