TOPIC: Can you help me figure out what the correct answer is and WHY?

Your boss comes into your office and wants the schedule estimate for your
project in which you have 99% confidence. If your worst case estimate is 10
months, your best case estimate 6 months and your most likely case estimate is 7 months what do you provide him?

A. 6.00 to 8.67 months
B. 6 to 10 months
C. 5.33 to 9.33 months
D. approximately 10 months

Dear Monique,

P = 10, M = 7, O = 6
beta estimate [(P+4*M+O)/6] = 7.333
sigma [(P-O)/6] = 0.667

Since the confidence level is 99%, it's 3 sigma (remember, 1 sigma = 68.26%, 2 sigma = 95.46%, 3 sigma = 99.73%, 6 sigma = 99.999%), so your range is beta+3*sigma and beta-3*sigma, which is 5.333 and 9.333 months.

Answer choice C is the correct answer.

If 95% confidence level, answer A would have been the correct answer.

Could you state where the question comes from?

O=6; M=4*7; P=10
(6+28+10)/6
=7,33

((O-P)/6)to the power of 2
((6-10)/6)^2
(-4/6)^2
1,33^2
=0,444*3 sigma(99%)
=1,333 3 std deviations

7,33-1,33
=6
7,33+1,33
=8,66

Answer is A 6 to 8,33

answer is c

Here, I will consider the formula for standard deviation. Not the formula for variance. So the correct answer would be "C".

Dear Charl,

Would like to point out that the sigma (standard deviation) formula that you are using is not correct: it should have been (P-O)/6. Secondly, by squaring the sigma (standard deviation), you are actually getting variance.

Other than that, I'd agree with your thought process.

Would like to know what other "experts" think of this one. Any suggestions are welcome!

Where did the power of 2 come from?
I've only ever seen the SD formula as
P-O/6 www(dot)pmpmath(dot)com/sd(dot)php

Also the square of 1.33 is 1.7689 not 0.444.

Can you help me understand where your numbers came from?

Aung, you are right!! This PMP question was taken from Career Academy PMP question bank..

But, do you think this type of question will ever be on the PMP... I finally see now why answer C!!

7.33+3(.667)=9.331 months
7.33-3(.667)= 5.329 months

Dear Monique,

Thanks for your reply.

When I took the exam, all formula questions are very straight forward - as long as you remember which formulas to apply.

As part of my test-taking strategy, I put all long, wordy questions and calculation questions to be the last to answer. Just see which strategy works for you.

Good luck with your preparation!

Aung Sint wrote: Dear Monique,

Thanks for your reply.

When I took the exam, all formula questions are very straight forward - as long as you remember which formulas to apply.

As part of my test-taking strategy, I put all long, wordy questions and calculation questions to be the last to answer. Just see which strategy works for you.

Good luck with your preparation!

Hi Aung Sint/Everyone,

Could you please advise why you chose the formula for PERT/Weighted average over simple average? The question didn't mention the use of the PERT method and hence I am a bit concerned to understand if we should by default use the PERT formula over the simple average (triangular) formula on the exam if the method is not specifically mentioned?

Questions are quite clear (unambiguous) which formula to use.

For me, during my preparation, the EAC questions are a bit confusing because you got 4 formulas to decide which one to use, and look for the key word or clue for the correct formula to apply.