PMP question

Discuss PMP doubts, tips and lesson learned. iZenBridge makes PMP® Certification easy
anuragca24
Posts: 3
Joined: Tue Aug 25, 2015 5:26 pm

PMP question

Postby anuragca24 Wed Aug 26, 2015 4:10 pm

37. A project manager has been asked by the client to meet the promise date of the project. The project manager analyzes the schedule before promising a date to the customer. The project manager uses the program evaluation and review technique to evaluate the project schedule. She decides that based on the PERT calculations she can promise a delivery date of June 30. The expected value of the project completion date is May 30. If the project manager is willing to accept a 5% probability that the project will be delivered later than June 30, what is the standard deviation of the duration of the activities on the critical path? Assume a five-day workweek.

a. Ten days
b. Fifteen days
c. One-half month
d. One month


what should be the answer and why? thanks in advance!
coolpmp69
Contributor
Contributor
Posts: 282
Joined: Mon Nov 17, 2014 8:55 pm

Re: PMP question

Postby coolpmp69 Wed Aug 26, 2015 8:43 pm

Expected date = May 30
probability of completing on or before June 30 = 95% confidence level
probability of completing after June 30 = 5% confidence level

To get 95% probability of a date less than June 30, you will need to add 50% of the area on the left side of the bell (normal) curve and 45% of the area on the right side of the bell curve.

PERT = [O+4M+P] / 6
O = 30 days * 95% = 28.5 days
M = 30 day * 50% = 15 days
P = 30 days * 5% = 1.5 day

So PERT = [ 28.5 + (4*15) +1.5 ] / 6 = 90 / 6 = 15 days

So correct answer is C - 1/2 month
anuragca24
Posts: 3
Joined: Tue Aug 25, 2015 5:26 pm

Re: PMP question

Postby anuragca24 Wed Aug 26, 2015 10:46 pm

Thanks!
However, I miss the part of distribution on the bell curve and how did you identify the % to apply. Can you refer the source or thread where I can get the understanding of this. thanks!
sachin07
Participant
Participant
Posts: 67
Joined: Tue Jul 28, 2015 5:47 pm

Re: PMP question

Postby sachin07 Thu Aug 27, 2015 9:15 am

Yes. I didn't understand it too. please suggest for reasons of distribution.

Regards
coolpmp69
Contributor
Contributor
Posts: 282
Joined: Mon Nov 17, 2014 8:55 pm

Re: PMP question

Postby coolpmp69 Thu Aug 27, 2015 1:18 pm

I learnt bell curve in my stats class so this was helpful. you can refer to this link to learn more about bell curve

http://www.dummies.com/how-to/content/b ... certi.html

BTW what's the right answer?
vivek3377
Super Member
Super Member
Posts: 391
Joined: Thu Sep 10, 2015 2:32 am

Re: PMP question

Postby vivek3377 Thu Sep 10, 2015 2:00 pm

Is it 15 days or 1/2 month? Both the options are given there.
coolpmp69
Contributor
Contributor
Posts: 282
Joined: Mon Nov 17, 2014 8:55 pm

Re: PMP question

Postby coolpmp69 Thu Sep 10, 2015 7:48 pm

I would go with 1/2 month instead of 15 days as the question mentions about month names (30 May - 30 June) rather than days (30 days).
vivek3377
Super Member
Super Member
Posts: 391
Joined: Thu Sep 10, 2015 2:32 am

Re: PMP question

Postby vivek3377 Thu Sep 10, 2015 10:08 pm

Is not an ambiguous question then? First of all it talks about dates. Then it talks about 5% probability of delay in delivering late of 30 June, which itself is 1 month delay from what customer expects.
Again it does not say how much delay from 30th June. 5% is probability and not % delay. So may be we cannot say that since there is 5% probability of delay, there is 95% probability of early delivery. We don't know how much 'early' or 'late'. So we do not have optimistic and pessimistic estimate.
I did not get the crux of the question itself. May be I have to revisit time estimation T&T.
Can you please explain it in more detail?
coolpmp69
Contributor
Contributor
Posts: 282
Joined: Mon Nov 17, 2014 8:55 pm

Re: PMP question

Postby coolpmp69 Fri Sep 11, 2015 1:29 pm

Agree...we don't' come across such questions in exam...not sure the source of this question. Some online pmp practice questions are of not good quality and make candidates dejected.
After solving even I was debating between picking 15 days vs. 1/2 months but ended up with latter one.. I would not worry about such questions but would concentrate on pmp exam preparation and be thorough with everything as much as possible..
vivek3377
Super Member
Super Member
Posts: 391
Joined: Thu Sep 10, 2015 2:32 am

Re: PMP question

Postby vivek3377 Tue Sep 29, 2015 5:16 am

I got some more clarification on this. It requires good amount of statistics knowledge.
In order for the project to have a 5% probability of being late, there is a 95% probability that the project will be delivered on time or earlier.
I found this statistical formula -

Code: Select all

We can determine the Probability associated with a Range. This Probability is also called the Confidence Level. The Statistical Distribution Theory provides Probability for different values of ‘n’.

If n=1 then Probability is 68.27%
If n=2 then Probability is 95.45%
If n=3 then Probability is 99.73%
If n=6 then Probability is 99.999999%

In terms of the PERT calculation this means that 2 standard deviations should be added to the expected value date of May 30. Since there is a one month difference between promise date of June 30 and the expected value of May 30, we can take optimistic day = 0 (first day - 30 May), pessimistic day = 30 (end day - 30 June).
So one standard deviation = (30-1)/6 = 4.83 i.e., 5 days
Based on above table, n = 2 should be taken.
So standard deviation is 2* 5 = 10 days (second sigma), which is one-half month.
This is a better answer than fifteen days because on the basis of a five-day work week this is close to three weeks.

Return to “PMP® Open Forum”

Who is online

Users browsing this forum: No registered users and 12 guests