You can apply PMP (project management professional) estimating techniques to resources, effort, duration, and costs. PMPs use different methods of estimating, depending on the situation.

Estimating method Description
Analogous estimating Generally used at the start of the project when not much is known. Compares the current project with past similar projects. A quick and relatively easy method of estimating, although not terribly accurate.
Parametric estimating Used for estimates that are quantitatively based, such as dollars per square foot or number of installations per day. A relatively simple method, but not every activity or cost can be estimated quantitatively.
Three-point estimating Accounts for uncertainty associated with estimating by determining an optimistic (best case, represented by O), most likely (represented by M), and pessimistic (worst case, represented by P) scenario. The most likely estimate is weighted most heavily.

The equation is
(O + 4M + P) / 6
Bottom-up estimating Used when there is significant detail about the activity. A detailed assessment of the resources, capabilities, and amounts are used to determine an accurate duration or cost estimate. This is the most accurate method but also the most time-consuming and expensive form of estimating.

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