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Calculating Variance of Activity the PMP way

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.

About Derek Huether

I'm Vice President of ALM Platforms at LeadingAgile. Author of Zombie Project Management (available on Amazon). Novice angel investor.

8 Responses to “Calculating Variance of Activity the PMP way”

  1. Poonam Bhogal
    November 12, 2010 at 11:08 am

    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
      November 12, 2010 at 12:41 pm

      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
        July 24, 2011 at 8:18 am

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

        • Anonymous
          July 24, 2011 at 11:55 am

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

        • chris baeckstrom
          April 17, 2013 at 8:33 am

          I’m reading Rita’s book and I see the formula but I don’t see any explanation of what activity variance means or what it is used for.

        • derekhuether
          April 17, 2013 at 11:54 pm

          Chris, it’s a quantifiable deviation from an expected baseline or estimate. Honestly, your “best guess” on an estimate may be just as accurate as a estimated calculated with activity variance. But, when it comes to the PMP, memorize it! See how it interacts with the other formulas you’ll also have to memorize.

  2. Ashok Prasad
    January 2, 2012 at 9:52 am

    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
      January 2, 2012 at 11:41 pm

      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.

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