Scenario: Your boss assigns a new project to you. She tells you it needs to be completed in 90 days. You create a work breakdown structure, identify all the task dependencies, and calibrate your minimum, most likely and maximum durations for each task.

You enter the tasks into MS Project, and enter you Min, Most Likely and Max values in the PERT table. MS Project calculates the duration of each task and the GANTT chart identifies the critical path tasks in red for you.

Knowing the tasks on the critical path, you calculate the standard deviation of the critical path.

Here is the information you have: MS Project tells you it will take 100 days to complete the project. You calculate the standard deviation of the critical path and get 7.5 days

What will you tell her is the probability of completing the project in 90 days?

What will you tell her is the duration of the project with a 90% confidence level?