Estimating effort: Part 3 Preparing three-point range estimations. It is important to understand the mechanics of preparing three point range estimates, especially if you are working alongside people who have never used this technique before. Just to remind you, we are still discussing effort estimates. Duration estimates will come later. Working one-on-1. Let’s take a simple example: You need to get an estimate of how much effort each team member will put into completing a particular activity. First, make sure you both understand the meaning of words like ‘estimate? You can also use?complete? It is tempting to ask, “How long do you think it will take?” This question will likely produce a time estimate, not an effort estimate. Ask the question “How many hours do you think this activity will take?” To ensure that you and your team members have a common understanding of the work, begin the discussion by reviewing the work. Decide how to deal with unknowns. Make assumptions, get answers, etc. Once you have reached a reasonable agreement, ask the person for their estimate of the effort required to achieve the best result. I use phrases like “If these assumptions turn out be true, how long do you think this work will take?” After they have answered that question, I ask them?if everything goes well, if this activity goes very smoothly, and still using the same assumptions how much effort do you think this activity is going to take? Then, I use similar language to get a pessimistic effort estimation. Be sure to keep your assumptions constant. The range of estimates will be very large if you have an optimistic estimate that everything goes well and a pessimistic one that assumes nothing goes well. Large ranges can make people feel uncomfortable as it suggests that they don’t understand the work. It will also be difficult to determine the accuracy of the range estimate later on because you will have to consider all the assumptions. It is likely that your first few conversations with a given person will not go smoothly. You may be asked additional questions or made to make further assumptions during the conversation. Fine. Let them. Assist them in climbing the learning curve. It takes most people about 3-5 iterations before they feel comfortable with the process. They will then give you three-point estimates. You can challenge their estimates but you should do so constructively and ask clarifying questions. Don’t cast doubts on their estimates. If your estimate is significantly different from theirs, it’s likely that your understanding of the work is different from theirs. Focus on identifying and resolving the differences. It seems important to ask for the most likely outcome first, then the optimistic, then the pessimistic. This sequence seems to work best, although I don’t know why. Working in a group. Your estimates won’t be developed one-on-1, but will be developed in small groups as part a team planning process. These small groups will still follow the same process:

  • Discuss and agree on the work that needs to be done.
  • Document the assumptions.
  • Start with the most likely result and create three-point range estimates.

Even if some members of the group don’t have deep expertise in the project’s work, their presence may help to uncover unstated assumptions. It can also help to build team commitment to the effort estimates and team understanding. There are other ways to estimate three-point ranges. Some project managers attempt to speed up the development of a 3-point range estimate by asking only for two numbers?the most probable and some form variance (e.g.,?10).