A project manager wants to estimate the time (number of days) required for completion of a project. From the manager's past experience, similar projects typically take 7 days to finish, but can be finished in 5 days given favorable conditions, and can take as long as 12 days if things do not happen as expected. The project manager wants to estimate the probability of finishing within 9 days.
The first step in selecting a probability distribution is matching available data with a distribution's conditions. Checking the betaPERT distribution for this project:
These conditions match those of the betaPERT distribution shown in Figure 95, BetaPERT distribution.
If that distribution is located in cell A1 and a forecast with formula =A1 is created, simulation results show there is about an 87% probability of the project completing within 9 days.
If the same forecast is calculated using a triangular distribution instead of a betaPERT, the probability of completing within 9 days is about 74% (Figure 96, Project duration based on betaPERT distribution).
