What are Project Assumptions?

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There may be inherent risks when we make project assumptions. We assume certain things to be true when in fact, they may not be. Consequently, we fail to challenge assumptions and continue planning and executing based on false notions. This can be costly.

An Example of Wrong Assumptions

So, how does this happen? In her book—Thinking in Bets—author Annie Duke shares an illustration:

Suppose someone says, "I flipped a coin and it landed heads four times in a row. How likely is that to occur?" It feels like that should be a pretty easy question to answer. Once we do the math on the probability of heads on four consecutive 50-50 flips, we can determine that would happen 6.25% of the time (.50 x .50 x .50 x.50).

The problem is that we came to this answer without knowing anything about the coin or the person flipping it. Is it a two-sided coin or three-sided coin or four? If it is two-sided, is it a two-headed coin? Is the flipper a magician who is capable of influencing how the coin lands?

In our projects, we may be guilty of this type of thinking. We may assume the world is flat when indeed, it is not. Assumption analysis can help us discover the facts or supporting information when identifying project risks and later when evaluating risks.


Definition of Project Assumptions

The Project Management Body of Knowledge (PMBOK®) 7th Edition defines assumption as "a factor in the planning process that is considered to be true, real, or certain, without proof or demonstration."

Assumption. A factor in the planning process that is considered to be true, real, or certain, without proof or demonstration. —PMBOK® Guide 7th Edition, page 235

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Four Common Assumption Mistakes

Individuals and teams make assumptions when planning or making decisions. As we consider different options, we choose the path that we believe will bring success. Let's explore common mistakes and what we can do about each.

  1. Failure to identify assumptions. Individuals and teams often make assumptions in subtle ways. They are not even recognized as such. When you hear or perceive an assumption being made, restate the assumption allowing everyone to hear the statement clearly. Furthermore, if you have an assumption log for a project or program, capture the assumptions.
  2. Not checking assumptions. Explore the validity of the assumption. Is the assumption accurate? Is it consistent with the facts? Additionally, where did the information come from? Is the source valid?
  3. Failure to assess assumptions. Dr. David Hillson, the Risk Doctor, says, "...not all assumptions matter equally...some assumptions might prove false." Hillson recommends the use of an IF/THEN test: "IF this assumption proved to be false, THEN the effect on the project would be..." The IF statement reflects probability and how likely the assumption is to be unsafe. The THEN phrase is about the impact or the significance. Record risks in your risk register where appropriate.
  4. Not considering alternative options. Assumptions are a way of dealing with uncertainty when we have different options. Are there other options that may reduce our risks?

"It’s not the things you don’t know that trip you up. It’s the things you think you know, but you don’t. You fail to ask a certain question because you believe you know the answer. Separating your information from your assumptions can be very tricky business." —Claudia Gray

How About You?

So, how about you? Are you making these mistakes? Take some time to review one of your projects. Ask your team members and key stakeholders where assumptions are being made. And capture those assumptions in an assumption log.

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