Exercise to calculate the delivery date of a project for a probabilityProbability Calculator - PERT Method

The following are the detailed calculations and graphs to obtain The time according to the data provided:

Step 1:

The PERT Method is based on two assumptions:

1. Project completion times follow a normal probability distribution.
2. The times of the activities are statistically independent.

From these assumptions, the normal distribution curve (Gaussian bell) is used to represent the project completion dates. This distribution will indicate that the project has a 50% probability of finishing before the Expected Time (T_E = 36.3333 days) and a 50% probability of exceeding the Expected Time.

To calculate The time where the project will be completed on schedule with a probability of 0.9 we will do the following:

Also:

Where:

• T: Due date to be evaluated.
• σ: Standard Deviation of the Project. It is obtained from the square root of the Variance.

Replacing the values we would have:

For a probability of 0.9 the value of Z is 1.2816. Therefore:

Note: The normal distribution table is used to calculate the Z value..

Within 39.2619 days, there is a 0.9 probability of completing the project on time.