Formulas To Remember For The PMP Exam

I think back to when I sat for the PMP exam and remember taking the first few minutes to quickly write down the following formulas.  It was my cheat sheet.  There was enough to think about for the next few hours and worrying if I could remember some key formulas was not one of them.  So, here is a bit of advice.  If you're preparing to take the PMP exam, MEMORIZE these formulas.  The exam won't come right out and ask you to identify the correct formula for a variance of an activity. Rather, it will offer a question like:  Your current activity was pessimistically estimated at 65 hours and optimistically estimated at 40 hours.  What is the variance of the activity?  (you can use this formula for both time and cost) You can see how knowing the formula is going to make you or break you on this question.

Do yourself a favor.  Make flash cards, get a tattoo, it doesn't matter.  Commit these formulas to memory and you'll save yourself some pain and suffering (and a few points on the exam).

The Formulas

Acronym

Title

Formula

PERT

Program Evaluation and Review Technique

P = Pessimistic Estimate M = Most Likely Estimate O = Optimistic Estimate

Standard Deviation of Activity

Variance of an Activity

Total Float

LS - ES or LF - EF

Communications Channels

[N(N-1)] / 2

CV

Cost Variance

EV - AC

SV

Schedule Variance

EV - PV

CPI

Cost Performance Index

EV / AC

SPI

Schedule Performance Index

EV / PV

EAC

Estimate at Completion

BAC / CPI

AC + ETC

AC + (BAC - EV)

ETC

Estimate to Complete

ETC = EAC - AC

VAC

Variance at Completion

BAC - EAC

CPI

c

Cumulative Cost Performance Index

Σ

EV /

Σ

AC

TCPI

To-Complete Performance Index

PERT Formula

PERT - Program Evaluation and Review Technique.If you’re going to take the PMP exam, you MUST remember this formula.  I’ve used it countless times in the real world and it works with surprising accuracy.

Formula: (P+4M+O)/6

Optimistic time (O): the minimum possible time required to accomplish a task, assuming everything proceeds better than is normally expected. Pessimistic time (P): the maximum possible time required to accomplish a task, assuming everything goes wrong (excluding major catastrophes). Most likely time (M): the best estimate of the time required to accomplish a task, assuming everything proceeds as normal.

How does it work?

Obtain three time estimates (optimistic, pessimistic, and most likely) for every activity along the critical path.  Plug your numbers into the formula and then sum the totals.  Though people will challenge you, you WILL have a more accurate critical path estimate.

I will speak to “Standard Deviation of an Activity” and “Variance of an Activity” at a later time.   They both leverage the same values but in different formulas.