Calculating Variance of Activity the PMP way

– December 28, 2009Posted in: PMP

When I was studying for the PMP exam, a few years ago, I remember memorizing a group of formulas. One of those was the “Variance of Activity.” At this point, don’t remember if it was even referenced in the exam. There were no direct questions asking “what is the formula for…” On my exam, I remember having numerous questions resulting from schedule variance calculations and cost variance calculations. To my surprise, I went searching for the Variance of Activity formula in the PMBOK (4th Edition) and I can’t find it! So as not to lead people astray when giving PMP study advice, I’m now researching each formula I was once told to memorize. I’m very surprised PMI didn’t save us a lot of trouble and list known formulas in the back of the PMBOK.

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Tags: Activity, Cost, Formula, PMBOK, PMP, Schedule, Variance

About Derek Huether

Agile Coach and Trainer. Co-Lead of the PMI ACP Support Team. Lover of Agile, Scrum, & Kanban. Lawfulgood PMP Level 15. Chaotic Good Agilist Level 5. Author of Zombie Project Management (available on Amazon)

Poonam Bhogal

Interesting observation Derek…I noticed the same and actually found it useful to read Rita Mulcahy’s book chapter for chapter for such gaps.
Poonam S Bhogal

Anonymous

Poonam, thank you for adding your recommendation. When people are prepping for the PMP exam, I always recommend they read Rita Mulcahy’s book. To the point of the formula, I do know that it’s a statistical formula. It’s so common, you can find it as a canned formula in Excel. I just come from the approach, when in doubt, put it in the book.

Bhaskar_rao33

Thanks Derek. The formula has typing error in Rita Mulcahy’s book. Rao

Anonymous

Wow, of all the typing errors to go to print, a formula? Ouch! Thank you, Rao, for pointing that out.

Ashok Prasad

If optimistic time
for an activity is 5 days, estimated time to complete the activity 85 and most
likely time 10 days. What is the variance of the activity?

Anonymous

The variance of the activity is still calculated by subtracting the optimistic time from the pessimistic time, dividing the difference by six and then squaring the outcome.