When you are developing the estimates for project, you choose to add the individual estimates...

Bottom-up estimating: Estimating the cost of individual work items and then rolling up the costs to arrive at a project total: It is more accurate. Analogous estimating: Analogous estimating is also called top-down estimating and uses the actual cost of a previous, similar project as the basis for estimating the cost of the current project. Parametric estimating: Using project characteristics (or parameters) in a mathematical model to predict costs (e.g., price per square meter).