PERT

PERT is a method to evaluate the required tasks in completing a given project, especially the time needed to complete each task, and identifying the minimum time needed to complete the entire project.

This technique is used for estimating and planning a project. Pert uses a simple statistical mathematics in order to come up with a probable date of the project milestones.

Tasks are estimated with 3 numbers:

Ø Optimistic (the best case)

Ø Most likely (the nominal case)

Ø Pessimistic (the worst case)

The three numbers are combined to come up with an expected duration. The following formula is used:

(Optimistic Estimate + (4 * Most Likely Estimate + Pessimistic Estimate)

___________________________________________________________

Divided by 6

The acronyms stand for:

Program
Evaluation
Review
Technique

Why would you use PERT?

I would use PERT in order to come up with an estimate for cost and duration in a project. This formula is great to use because the estimate is more accurate. As a project manager, I would also use PERT for planning and tracking the entire project. As we all know all projects have a start and end date and most of the shareholders are interested in knowing how long the project is going to take. PERT is said to be a tool to help reduce time and cost required to complete a project. It also helps to identify any critical path and gives project managers a better understanding of dependencies and tasks duration. PERT would help me manage and control very large and complex projects.

Please describe in detail using your own words. I am not interested in calculations.

Optimistic

Optimistic time is generally the shortest time we think a project may last. In other words, this is the time that project managers think a task will take in order to be completed without encountering any problems.

Optimistic is the minimum time required to complete a task. This time is set by anticipating the best possible outcome without considering any interruptions, trouble, or catastrophes.

Most likely

Most likely is the time with the highest probabilities. In other words it is between optimistic and pessimistic. The most likely time considers any normal situations that the project might encounter; therefore is a little more than the optimistic time. Most likely might be the best estimate of time required to complete a task.

Pessimistic

Pessimistic is the longest time we think a project can take to complete. Sometimes projects don't go as planned and things go wrong, therefore the time is prolonged.

Pessimistic is the maximum time required to accomplish a task. For instance; to paint the outside of a house might take 3 days but this time has been set from previous experience where no problems or difficulties got in the day. But what about if it rains? This is something unexpected that may delay/extend the task duration.

Expected duration

The expected duration is the combination of these three numbers by using the following formula:

Expected time = (Optimistic + 4 x Most likely + Pessimistic) / 6

By using this formula the expected duration is more accurate since we have taken into consideration opportunities, problems or any other situations. The expected time could also be called "weighted average".