When a schedule with acriviries that have uncertainty associated with their durations is encountered, the PERT method can be used to help predict the probability and range of values that will encompass the actual duration of the project. While the PERT technique uses the normal and beta distributions to determine this probability and range of values, there is a serious flaw in the results. The assumption made in the PERT analysis is that the critical path of the project remains the same under any of the possible conditions. This is, of course, a dangerous assumption. In any given set of possibilities it is quite possible that the critical path may shift from one set of activities to another, thus changing the predicted completion date of the project.
In order to predict the project completion date when there is a possibility that the critical path will be different for a given set of project conditions, the Monte Carlo simulation must be used. The Monte Carlo simulation is not a deterministic method like many of the tools that we normally use. By that I mean that there is no exact solution that will come from the Monte Carlo analysis. What we will get instead is a probability distribution of the possible days for the completion of the project.
Monte Carlo simulations have been around for some time. It is only recently that the use of personal computers and third party software for project management has become inexpensive enough for many project managers to afford.
In order to predict the project completion date when there is a possibility that the critical path will be different for a given set of project conditions, the Monte Carlo simulation must be used. The Monte Carlo simulation is not a deterministic method like many of the tools that we normally use. By that I mean that there is no exact solution that will come from the Monte Carlo analysis. What we will get instead is a probability distribution of the possible days for the completion of the project.
Monte Carlo simulations have been around for some time. It is only recently that the use of personal computers and third party software for project management has become inexpensive enough for many project managers to afford.