Estimating Activity Resource Requirements
The resource requirements for an activity are estimated by using the Estimate Activity Resources process.

The main purpose of this process is to accomplish the following goals:

Estimate the types of resources needed for a given activity
Estimate the quantities of each type of resource needed for the activity

Figure 4.6 shows the Estimate Activity Resources process with its input, tools and techniques, and output.

figure 4.6.png

The activity list and attributes determined by the Define Activities process are the major input items to activity resource estimating.

Input to Activity Resource Estimating

The activity list and attributes are the obvious and major input to the activity resource estimating process. These and other input items are discussed in the following list.

Activity list and activity attributes. The activity list originally developed during the activity definition process identifies the schedule activities that need the resources. The activity attributes provide the details for the activities, which will be helpful in estimating the resources.
Resource calendars. Resource estimating will require information on the available quantity of resources of different types, such as human, equipment, and material. This information is usually available in the resource calendars, which may also have detailed information about human resources, such as skill level, experience, and the geographical location from where the resource will come. Typically, the resource calendar contains the following useful information about the resources: Days and times of day when a resource is available The passive time for the resource— for example, holidays for human resources The quantity of each type of available resource The capability of each resource
Enterprise environmental factors. Information about the infrastructure of the performing organization, such as existing facilities, will be used in identifying the resources and their availability.
Organizational process assets. The organizational process assets useful for activity resource estimating include organizational policies for staffing and purchase of supplies, historical information on what types of resources were used for similar activities in a previous project, and the like.

Once you understand the activities, you can use some tools and techniques to determine the resources required to perform those activities.

Tools and Techniques for Activity Resource Estimating
Following are the tools and techniques used to determine the resources required to perform schedule activities.

Alternative analysis. Alternative analysis is all about exploring alternative solutions to a problem. In the case of estimating resource requirements, you will need to consider alternatives available for resources needed for some schedule activities. For example, you might need to decide whether you want to buy or develop a tool needed to perform an activity, what types of machines (for example, Windows or Linux) to use, which computers to use to do the development, or what level of skills is needed.
Bottom-up estimating. You might discover that it is rather complex to estimate resources for a given schedule activity. If the problem is inherent to the activity, it might be helpful in certain cases to decompose the activity into smaller components for the purpose of resource estimating and, then estimate the resource for each component, and then aggregate the resources to get an estimate for the whole activity. In aggregation, you must consider the possible relationships (overlaps and such) among different components of the activity so you don’t double-count the resources.
Expert judgment. Expert judgment can be used to assess the input and determine the output of the resource estimating process.
Published estimating data. Information published by various vendors, such as costs for resources, can be useful in estimating the resources. Project management software. Depending upon the sophistication of the resource requirements and the capabilities of the available features, project management software might be useful in estimating and managing the resources. It can also be used to create resource breakdown structures.

You can use a combination of these tools and techniques to generate the output of the resource estimating process.

Output of Activity Resource Estimating
The resource requirements are the major output of the resource estimating process. These and other output items are discussed in the following list.

Activity resource requirements. The main purpose of the activity resource estimating process is to determine the resource requirements for each activity, and therefore this is the major output item from this process. You identify the types of resources required to perform each activity and estimate the required quantity of each identified resource. If a work package in the WBS has multiple activities, the resource estimates for those activities can be aggregated to estimate the resource requirements for the work package. The requirement documents may also include information such as the basis for each estimate, the assumptions made for the estimate, and the availability of the resources.

Resource breakdown structure. The resource breakdown structure (RBS) is a hierarchical structure of resource categories and types required to complete the schedule activities of a project. The RBS can be used to identify and analyze the project human resource assignments.

Updates to project documents. The identified types of required resources for an activity and the estimated quantity for each identified resource become activity attributes and must be added to the attribute list for the activity. Activity resource estimating might generate modifications to the activity list— for example, to add or delete an activity. It may also cause you to change the resource calendar.

Once the activities have been identified and resources required to perform each activity have been estimated, you have enough information to begin estimating the time needed to complete each activity, which is called the activity duration.