# Thread: Most optimistic, pessimistic, likely times (98)

1. ## Most optimistic, pessimistic, likely times (98)

In project management classes, they teach using the most optimistic (a), most pessimistic ([img]/forums/images/smilies/cool.gif[/img], most likely times (m) so that you have three time estimates and can estimate variability. You then calculate expected time as

(a + b + 4m)/6

and activity variance as

(b-a)^2/6

Does Project allow you to enter times in this fashion and then compute the variances and probabilities?

2. ## Re: Most optimistic, pessimistic, likely times (98)

Project will allow you to enter calculated fields, however, where would the times (a, b, m) be coming from? Project has the early / late start and finish fields as well as baseline data but I don't see how this would help.

Could you explain where your class gets the times from?

3. ## Re: Most optimistic, pessimistic, likely times (98)

A, b, and m are standard project management theory. A is an estimate so fast that you only have a 1% chance of beating it. B is an estimate so slow you only have a 1% chance of exceeding it. M is the most likely time.

Ronny

4. ## Re: Most optimistic, pessimistic, likely times (98)

It sounds as if you would need a project add on package that calculates risk. I don't know how you would track or enter the A, B, and M in project without other software.

Good Luck.

5. ## Re: Most optimistic, pessimistic, likely times (98)

Ronny:
There is a PERT analysis toolbar that can help you calculate what you are looking for. If you right click on your toolbar you will see the PERT Analysis. Once that is up you can analyze either a single task or all of them. For a single task, you select it and click on the green button (pert entry form). YOu can enter in your opt., Pess, and your expected, click ok and then click on the calculator button on the toolbar, which will calculate (opt + Pess + 4M)/6. They claim it is within a 5% probability. You can adjust the weights of your equation so that it is weighted more heavily on the pessimistic side by clicking on the scale button and changing the pess. to 4 and the exp. to 1...and recalculate. The values are all saved in the custom start/finish fields as well as the custom duration (1-3) fields. If you had 2000 version, you could then create a formula in another duration field that would calculate various probabilities...but 98 wont allow for that.

6. ## Re: Most optimistic, pessimistic, likely times (98)

This is great. I don't know how I missed it but it's right there. Thanks.

Ronny

7. ## Re: Most optimistic, pessimistic, likely times (98)

... Tanya,

I get to learn something new every day. Using the Pert to do this is not what I would have expected.

Thanks

8. ## Re: Most optimistic, pessimistic, likely times (98)

Cool! Glad I could help. Isn't learning fun? <img src=/S/clapping.gif border=0 alt=clapping width=19 height=23>

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