Exercise to calculate the probability of finishing a project on timeProbability Calculator - PERT Method

Problem Data

It is required to calculate The probability that the project will be completed in less than 40 days according to the following data:

Expected Project Time (TE)
36.3333 days
Project Variance (σ2)
5.2221
Description
Exercise to calculate the probability of finishing a project on timeYou have a project with an expected completion time of 36.333 days and a variance of 5.2221. You want to know the probability of completing the project in less than 40 days.

Solution

The following are the detailed calculations and graphs to obtain The probability 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 (bell curve) 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 (TE = 36.3333 days) and a 50% probability of exceeding the Expected Time.

To calculate The probability that the project will be completed in less than 40 days we will do the following:

Also:

Where:

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

Replacing the values we would have:

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

The probability that the project will be completed in less than 40 days es 0.9457

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