 As a project manager or as project team member, you need to make more than one estimate during the project.

• How long will it take to complete ?
• How much will it cost to realise ?
• etc

Those who make the decision need to make sure their estimations are as accurate as possible, so how can you reflect "certainty" or "uncertainty" in your estimates?

I recently discovered an interesting tool developed by William W. Davis, MSPM, PMP, the Project Management Superhero , to get this done easily !

#### Estimating or guessing ? That's the question.

Making an estimate might look like guess work, but when you have your facts and figures under control it will become a well calculated estimate instead of a "guesstimate".

William W. Davis has bundled his expertise into a Microsoft Excel sheet or workbook. He combines the classic 3-point PERT (Project Evaluation and Review Technique) with some statistical mathematics.

#### Classic 3-point estimate

The classic PERT uses three values to calculate the estimate value :

• minimum (MI),
• most likely (ML),
• maximum (MA)

The estimate value is then calculated as  : (MI + 4xML + MA) / 6

This is pure mathematical and thus not reflect any certainty or uncertainty about the 3 base values MI, ML, MA.

#### The SPERT method developed by William

The additional "S" does not come from SuperHero or SuperPower, but it relates to Statistics and Sensing.

Statistical PERT is a five-step process (but a SPERT template makes it only three steps). The five steps are:

• Identify a minimum, most likely and maximum outcome for some uncertainty
• Calculate the expected value using the PERT formula
• Make a subjective judgment about how likely the most likely outcome really is
• Calculate a standard deviation
• Choose any probabilistic estimate that fits your desired risk level

SPERT templates do steps 2 and 4 for you, and Excel’s statistical functions in Step 5 make that a snap.

#### FREE !

William offers all Statistical PERT example workbooks and templates, for free, to everyone. 