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PMP Process – Estimate Activity Resources 

 September 15, 2021

By  Dave Litten

PMP Process – Estimate Activity Resources

This is a process where you look at each individual activity and determine what and how many resources are needed to accomplish that activity. Resources are not just people, but also include equipment, machines, and different types of supplies needed to finish the activity.

This process lists all the resources, both physical and staff, and how many of those resources are needed.

PMP Process - Estimate Activity Resources Management

This particular process focuses on each activity within the schedule to calculate the resource requirements. Another factor that will need to be considered along with the hours’ work effort required, is the availability of the resources.

All of the above will combine and result in the project schedule which is developed in a later process within the time management group.

There is a fundamental formula that ties together the duration of an activity against the amount of work effort required, and the resources needed to complete that work within the estimate activity resources process:

Activity duration = work effort/human units. For typical activities the duration will be measured in days, the work effort in hours, and the number of people required as a decimal fraction.

PMP Process - Estimate Activity Resources Management

Although the Estimate Activity Resources process forms part of developing the project time schedule, this process is normally undertaken in parallel with the process ‘estimate costs’ (which is a process within the cost management process group).

Inputs used to estimate activity resources:

Project management plan. This will contain the resource management plan, which will give guidance on how to perform this process. It will also contain the scope baseline which is made up of the project scope statement, WBS, and WBS dictionary

Activity list. This is the prime input to estimate activity resources because each activity in the list will be studied so that appropriate resources can be estimated.

Activity attributes. These attributes will often include activity information such as the knowledge, skills, and experience for suitable individuals to carry out the activity. It may also include information on nonhuman resources such as facilities, and materials, and tools.

Assumption log. This will keep track of any assumptions that are made during the project. Assumptions and constraints could affect how the schedule is built and may impact the lead and lag between activities.

Resource calendars. This will cover both human and non-human resources as the availability of an individual and then normal working hours will be just as important as the availability of resources such as a facility or heavy plant machinery as an example. This availability will need to be factored into each activity and may have a bearing on the duration of each.

Enterprise environmental factors. Examples of why this may affect the resources required for an activity could be the laws and regulations resulting in more or less work effort to carry out each activity, the environment within which the activity is to take place, or even the logistics concerning the use of resources.

Organizational process assets. Typical assets might be data from previous similar projects regarding the work effort for typical activities, or procedures that are mandated to carry out particular activities.

Outputs from the estimate activity resources process:

Activity resource requirements. This is normally a document that describes the number of resources for each scheduled activity, and the knowledge, skills, and experience of each. The work effort may be described as total hours, or as skills set per time period. An example for the latter might be three bricklayers for a period of two weeks. It is helpful to include assumptions and other detail in support of such estimates for each activity.

Activity resource requirements will document the number and types of resources needed to complete each activity. This should be very detailed. For example, if you are painting a room, this process would list the resource requirements as two painters, 4 gallons of primer, 2 gallons of glossy white paint, two rollers, one roll of tape, one tarpaulin, and four paintbrushes.

Basis of estimates. This is a document that outlines what was used to create the estimates pertaining to the resources on the project and how the estimates were created. For example, what methods were used to develop the estimate, what assumptions and constraints were made, and the range of the estimates.

Resource breakdown structure. This is known as the RBS and is a similar graphical diagram to the WBS, however, the diagram and each node describe the resources by category and type. A particular project may split the categories by knowledge or skills, or by department or group.

PMP Process - Estimate Activity Resources Management

This is a hierarchical breakdown of resources by their categories and types. On a phone system upgrade project, you can break down resources by software, hardware, and people. An RBS can help track project costs as it ties to the organization’s accounting system.

Project document updates. It is highly likely that the activity lists and activity attributes would normally get updated as a consequence of estimating activity resources. The resource calendars may be modified as well to pre-assign such resources.

Alternatives analysis. When considering the resource requirements for each activity (estimate activity resources), it may be helpful to consider alternative ways of carrying out the work as well as the resources needed to do so. This may result in a more effective and efficient way to carry out the activity such as buying procurement rather than designing in-house.

Expert judgment. As with all things in life, nothing beats experience. Those who are considered experts, or even those who have carried out similar tasks, should be involved in all aspects of estimating as this will result in a more realistic and achievable set of activities within the estimate activity resources process and the resulting schedule.

Published estimating data. This is often available in two forms; internal published sources based on historical data and experience of carrying out similar activities and industry-standard tables of resources and effort. Within the building industry, for example, there are standards tables describing the amount of person-effort to construct standard frames when erecting buildings. Another example is the number of bricklayers needed to create a wall of standard dimensions.

Project management software. Applications such as Microsoft Project can assist in storing and structuring information and will allow swift calculations of alternatives or schedule possibilities. Such software is only a tool, however, and the phrase ‘garbage in – garbage out applies here!

The documents you are most likely to use in this process include:

Risk register. This would list all the identified project risks, as well as their impacts and response. Risk responses can lead to adding reserve time to activities.

Cost estimates. These will be the individual costs that are assigned to each activity. Knowing the cost of an activity will be critical to determining what resources should be used on the project.

Expert judgment. This is a helpful tool when dealing with resources. If you are painting a room and need to estimate how much paint will be needed, then it would be best to ask a painter who would be your subject matter expert.

Tools and Techniques

Bottom-up estimating is when you break down the activities in more detail until you can assign the resources. You can then aggregate them back up to the full activity. This form of estimation requires the work to be very detailed before it can be done.

PMP Process - Estimate Activity Resources Management

This is considered one of the best estimates to use because it is very accurate, but it is also very time consuming

Analogous estimating. This is also known as a top-down estimation. It relies on historical information to assign the current duration to the activities. It is based on a limited amount of information. This is a quick estimate, but because you’re not actually inspecting the work, it may not be very accurate.

PMP Process - Estimate Activity Resources Management

Parametric estimating. This uses a mathematical algorithm to calculate costs or duration. The calculation is based on historical data and variables. For example, if it takes one programmer to write one module, then it will take 10 programmers to write 10 modules. This form of estimation could be accurate depending on the accuracy of the data that is used to calculate it.

PMP Process - Estimate Activity Resources Management

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Dave Litten


David spent 25 years as a senior project manager for USA multinationals, and has deep experience in project management. He now develops a wide range of Project Management Masterclasses, under the Projex Academy brand name. In addition, David runs project management training seminars across the world, and is a prolific writer on the many topics of project management.

The Projex Academy

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