Estimate Activity Durations Process

Estimate activity durations process is a project management process that must be implemented before creating a project schedule and allows us to achieve the output of duration estimates that are used as a cornerstone in determining the final schedule. In PMBOK 7 estimating is a part of planning performance domain.

The process of estimating activity durations is basically the process in which we anticipate how soon we will complete a planned task with estimated resources derived from the previously conducted estimate activity resources process. The estimate activity durations process is considered in;

This process is conducted continuously throughout a project. 

How to Estimate Activity Durations?

In order to be able to accurately predict activity durations, we need to have inputs such as a schedule management plan, resource estimates, and resource calendars. Of course, it is important that we have a list of activities and a document of activity characteristics in order to know which activities we will predict.

As with activity sources, a number of commonly used estimation methods are used when estimating activity times. These techniques are analogous estimating, bottom-up estimating, parametric estimating, three points estimating. Also, expert judgment is a very useful tool to take the opinions of people who had experience in similar tasks. Similar techniques will be used in estimate costs and estimate activity resources processes.

Outputs Created in Estimate Activity Durations Process

  • Activity duration estimates: This is the main output of the estimate activity durations process. We will use these estimates to create a schedule later.
  • Basis of estimates: In this process, we will have some estimates at the end. However, archiving the basis of the estimates to justify them will make our project more trackable.

Inputs of Estimate Activity Durations Process

  • Activity list: This is our main input as we will estimate activities from this list.
  • Activity attributes: Along with the activity list, we will use activity attributes because while making estimations we will desperately need the attributes of activities. These characteristics may affect the estimation from low to high degrees.
  • Schedule management plan: Since this is a process of schedule management knowledge area, this plan will provide us guidance to conduct this process.
  • Scope baseline: It is used in this process to control and validate if the resources are enough to produce deliverables and work mentioned in the scope baseline.
  • Assumption log: In estimations this log is used for evaulating conditions such as availability of the resources or the cost of the resources.
  • Resource calendars: This input illustrates which resources, tools and techniques will be available at specific time intervals. While estimating the durations of activities you have to take the availability of them into consideration.
  • Risk register: You should be aware of possible risks to make a close estimate.
  • Enterprise environmental factors: Factors such as databases of estimations, metrics of productivity, commercial publishments or location of team members can be given as an example of EEF's recommended to use in this process.
  • Organizational process assets: Historical information about durations of similar activities, project calendars of the organization, existing policies and procedures and lessons learned repository are examples of OPA for this process.
  • Lessons learned register: It consists of previously learned lessons and knowledge gained from previous phases about the duration.
  • Milestone list: As it shows us the specific milestone dates to be achieved, it would be helpful for us to determine the activities that lead to milestones.
  • Project team assignments: The specialties of the project's human resources have a direct effect on activity durations. The training level, the reason for assignment, the expertise level of the team are useful indicators for estimations.
  • Resource breakdown structure and Resource requirements: The resource types and requirements are useful to know while estimating durations.

Tools & Techniques of Estimate Activity Durations Process

  • Analogous estimating: It is simply done by using the information from a similar previous project or projects from the organization’s historical data. It is also known as top-down estimation. It is useful when we aim to get a rough estimate in a limited time.
  • Parametric estimating: This technique is used when the historical data from the previous projects are available. To do this, historical data needs to be analyzed and converted into parameters for estimations.
  • Bottom-up estimating: It is the technique where you simply decompose the work to be estimated into the smaller units until it is the easiest to estimate as a small unit. After doing this aggregating the estimates can give the estimation of the total. It is very useful when we seek for a close estimate.
  • Three-point estimating: While doing this you have to determine 3 different points as minimum, maximum and most likely. 
  • Alternatives analysis: This technique is used for the decisions amoung alternatives and to fit these alternatives to the milestones and requirements of the project. This decision may affect the estimation.
  • Reserve analysis: For identified and non identified risks of the project, some extra time is kept aside as duration reserve. The analysis of this reserve is a technique in this process.
  • Voting: It is a very well known decision making technique. In Schedule management plan you can determine if you will seek majority or unanimousity for the decisions.
  • Meetings: As always, meetings are a useful tool for sharing of information.
  • Expert judgment: Anyone with knowledge about the activities or techniques to use can be used as experts. This may be team members in the project, an estimation expert, an independent consultant, or another project manager with historical estimation experience.

Comments:
1- Engus 04.06.2021
Thank you very much. I appreciate your work here. Even though all processes about estimation seem similar, i think there are much juice from the essence to take. For this reason such explanations are valuable.