PERT ESTIMATING TECHNIQUE
Determining the time needed to complete a task is difficult. An unlimited number of variables are involved, making it impossible to completely account for them. The best approach is to develop an estimate that you have a high level of confidence in reaching. The PERT (program evaluation review technique) estimating technique can help you do that.
The PERT estimating technique involves the use of three variables for calculating the overall time to complete a task. The three variables are the most optimistic, most pessimistic, and most likely times.
The most optimistic (mo) estimate is the time needed to complete a task under the best conditions. The most pessimistic (mp) estimate is the time needed to complete a task under the worst conditions. The most likely (ml) estimate is the time needed to complete a task under normal conditions.
The PERT estimating technique offers several benefits. One, it gives more reliable estimates. Two, it is easy to calculate, although it is time consuming. Three, it is superior to other estimating techniques.
The variables are used for the expected time. The expected time is then adjusted to account for nonproductive time (e.g., time for going to the restroom, chatting about nonwork-related topics).
for Using the PERT Estimating Technique
Develop a complete work breakdown structure.- For each task, determine most pessimistic, most likely, and most optimistic times.
- Note: Do this for only the lowest levels of the work breakdown structure.
- Calculate the expected time for each task.
- Example: Most optimistic time is ten, most likely is twenty, and most pessimistic is thirty.
- Estimate the percent of nonproductive time.
- Calculate the adjusted expected time for each task.
Adjusted Expectedtime = (Nonproductive Time) x (Expectedtime)- Example: Nonproductive time is 10 percent (or 100 percent plus 10 percent, which equals 110 percent or 1.10).
Adjusted Expectedtime = 1.10 x 20 = 22 Hours Adjusted Expectedtime