Activity Resource Estimating
Activity resource estimating is the process of defining resources (people, equipment, material) needed for the schedule activities. This includes what, when, and how many resources are needed for the various project activities. The activities attributes are the main input for this information.
Activities attributes, an output of activity definition, are descriptive terms and definitions used to describe codes, predecessors, successors, constraints, person responsible, geographical location, level of effort, lead and lag, imposed dates, assumptions, and so on. Organizational process and environmental factors influence resource estimating by limiting and controlling how you acquire and use resources.
Most project managers will use a combination of techniques to develop the resource estimates. Two of the most used are bottom-up estimating and expert judgment. Bottom-up takes the lowest level of the decomposed WBS and rolls up these tasks to the next level. For example, if you have only two tasks on a lower level that both take two days to complete, the summary task at the next higher level will take four days because it sums the numbers below it. Mature industries may have published estimating data that contains extensive data on all sorts of metrics for capabilities, type of machines, different tools, and so on. Some examples are feet of pipe laid per hour or the standard time it takes to do a brake job for a Ford Taurus. Of course, most project managers use some type of project management software to help with this estimating because it can help organize all the resource inputs.
The resource estimates are useful for identification and documentation of resource requirements used for each activity and any specialized knowledge and level needed. Resource calendars describe resource availability and allocation allowed. Resource Breakdown Structure (RBS) is a hierarchical structure of the identified resource by category and type (PMBOK, p. 138).