Statistical Ideas Related to Network Diagrams

When dealing with Network Diagram questions on the PMP exam you may be asked to perform some statistical analysis on the data that you either find or is provided to you. This section focuses on giving you all the information you need to answer these types of questions.

Three Point Estimating

When estimating activity durations or costs the accuracy of a single estimate may not be good enough.  At that point we may go to a three point estimate.  The three point estimate looks at the:

• Most likely Estimate (ML)
• Pessimistic Estimate (P)- sometimes called worst case
• Optimistic Estimate (O)-sometimes call best case

To calculate duration (or cost) estimates with three points we may use:

Standard Deviation and Variance for an Activity

Standard Deviation is a measure of the amount of variation we have in a set of data. The larger the standard deviation the larger the variation.  The smaller the standard deviation the small the variation.

To calculate Standard Deviation or Variance given Most Likely, Pessimistic, and Optimistic Estimates for the duration of the activity:

Standard Deviation and Variance for a Path

These ideas when applied to a path are very difficult and don't represent the difficulty of the PMP exam. That said, they could be tested so I have included them here. Use these as practice for mastering your calculations when dealing with an Activity.

There are six possible steps when dealing with Standard Deviation for a path:

1. Determine the Duration Uncertainty for each activity
2. Determine the Standard Deviation for each activity
3. Determine the Variance of each activity
4. Determine the Project Variance for the remaining path
5. Determine the Standard Deviation for the remaining path
6. Determine duration uncertainty for the remaining path