How to carry out an assessment on three points?

You should learn how to evaluate the terms of tasks at three points, as this is, of course, the best technique for assessing the duration of work together with members of your project team. The technique is called a “three-point assessment” because team members give a pessimistic, optimistic and most likely estimate of the completion time. This technique is one of the best approaches, as it allows the project manager to achieve the following:
  1. Improve accuracy over single point estimates.
  2. Improve the commitment received from the team because the assessment takes risks into account.
  3. Get useful risk information in each task.

Three-point assessment is a three-step process

  1. We work with a team member who will perform the task to determine both positive and negative risks associated with his task. Negative risks are those that can increase the term of the task, and positive ones can be reduced.
  2. Then we ask the team member to name three ratings. The first is the most probable (BG), which is the average duration of work on a task if the employee does it 100 times. The second assessment is pessimistic (P) - the duration of work on the task if all the negative factors that we identified work out. Finally, we ask you to give an optimistic assessment (O) that takes into account all previously identified positive factors.
  3. Now we carry out simple calculations with three estimates obtained. We calculate the value and standard deviation using three-point estimation formulas: (O + 4 * BG + P) / 6 = weighted value, and (PO) / 6 = standard deviation (used to calculate probabilities). The weighted value for the three evaluations that a member of the team gave us is the estimate that we use for his task. It takes into account the risks in the task and the effects of positive and negative risks.

Discussing the risks in the task, we give the employee the opportunity to participate in the process of determining the assessment. We also bypass the games that usually occur when evaluating a single value. Usually in the process of determining this single value, team members stretch it as soon as they can. They know from experience that the project manager is likely to arbitrarily cut it. It’s for sure that this is not a way to get a good grade.

When we evaluate at three points, we record all three ratings in the relevant documents, as well as the positive and negative risks identified for the task. We openly inform the project team and customers that the estimates are not 100% accurate. That there are risks that we have considered and which may affect the time taken to complete the task. This approach eliminates some doubts of the team members regarding the task assessment process.


A three-point assessment provides us with better information, as we explicitly take risks into account. In addition, we learn about the risks of the task in the early stages of the process and learn from who will carry out the task. All this gives us the opportunity to take corrective actions before the work is started. This increases the likelihood of good risks and reduces the likelihood of bad ones.

For example, a team member says that when performing work that involved a certain department of the company, the amount of work increased significantly due to the fact that the leaders and managers of this department constantly missed appointments. Knowing this, we can take steps to ensure that representatives of this department attend the meetings. We can even attract a project customer to get a promise from them to attend meetings. If we can reduce the likelihood of negative risks, then we are taking a big step towards improving the terms of the project.

Author: Dick Billows
Original article: How to do 3-point Estimating
Additional Resources: PERT

Also popular now: