Expected Project Duraction and Project Standard Deviation

JWP

Thanks to Rita Mulchahey's PMP Exam Prep 7th Edition I now understand the formula process for solving the activity standard deviation range of estimate for the activity. However, when I worked the problem for the overal project duration I calculate that standard deviation for the problem on page 192 in her book is 16.667 but the answer key in the book for project standard deviation is 10.060. More than likely I am wrong but I do not understand why. I would appreciate anyone's help in setting me straight.

JWP

My sincere apologies to anyone who may be looking at this. I read on after spending way too much time being stuck on bad assumptions and now see the key to the solution and understand where I went wrong (adding the individual deviations). My question now is, is there any known history where the exam asked specifically to solve an example project standard deviation and project range of estimates?

Harwinder

@JWP

Welcome to PM Hangout. I think there's a very little chance that you'll get a question that requires lengthy calculations similar to those in Rita's book. But you may be required to calculate SD/variance of an activity. It's still good to know the calculations and play safe.

Hope that helps.

JWP

Thank you Harwinder!!