PMP BLOG

Three Point Estimate

 

                                                                                             Three Point Estimate

 

PERT (Program Evaluation Review Technique) is the most common form of three-point estimation. It’s a technique that was developed in the 1960s by consulting firms working with the U.S. government as a way of getting more accurate project duration predictions up front. To do a PERT estimate, you start with three estimates—pessimistic, most likely, and optimistic estimates. Since the pessimistic and optimistic estimates are less likely to happen than the normal estimate, the normal estimate is weighted (multiplied by 4) and added to the optimistic

And pessimistic estimates, and then the whole thing is divided by 6 to give an expected duration. The formula looks like this:

(Optimistic duration + 4 most likely duration + Pessimistic duration) /6=Expected Duration

 

Excersise

1. A software team gathered estimates for all of the work they’d have to do to build the next major release of their
flagship product. Last time it took them around 45 days, but they’re hoping that the lessons learned from the past
release could bring the time down to 30 days. However, the infrastructure team needs to upgrade their servers, and
they are concerned that procurement delays could potentially extend the project out to 90 days.

Expected duration = __________ Optimistic duration = __________ Most Likely duration = __________
Pessimistic duration = __________

2. A construction team gathered estimates for all of the work they’d have to do to build a garage. In general, they can
build a garage in 20 days, but rain or cooler temperatures could stretch the project out to 30 days. If, however, the
forecast is correct, warm, sunny weather might bring the duration down to just 12 days.

Expected duration = __________ Optimistic duration = __________ Most Likely duration = __________
Pessimistic duration = __________

3. A project manager used data from past projects to come up with an estimate for an upcoming software system
replacement project. She felt confident about a 25-day duration, but also noted that adding an extra resource could
bring the schedule down to 10 days. The test team felt that the complexity of some completely new features would add
additional test cases, adding a few weeks for a 40-day estimate.

Expected duration = __________ Optimistic duration = __________ Most Likely duration = __________
Pessimistic duration = __________

4. A project manager in charge of a big civil engineering project came up with an estimate for a highway re-paving
project. The worst-case scenario was 82 days, but the team felt more certain based on past experience that they could
get it done in 49 days. If all went well with their equipment and materials, it might be done in 33 days instead.
Expected duration = __________ Optimistic duration = __________ Most Likely duration = __________
Pessimistic duration = __________

image_pdfDownload Page

Related posts

Leave a Comment