Facts about success of software and IT projects: Numbers remain »constant« for 20 years
Source: Chaos Report-Studie, Standish Group 2012-2015
Heuristic (top-down, bottom-up) and parametric sizing methods are used to objectively determine the size of a project. Parametric methods meant functional sizing (FS) methods, "hard-facts" or, according to the ISO standard, FSM (Functional Size Measurement).
FS methods have a different number of specific metrics. With these metrics, functional & qualitative requirements are transferred to unitless numbers (size), usually called points. All FS methods return as result just a size, but not effort, duration, or cost.
Typical examples of FSM methods are, e.g. Use Case Points, Story Points, Feature Points, Function Points, COSMIC Points, SNAP Points, MKII Points, etc. Further, there are specific FS methods, e.g. RICEW Points (for sizing of ERP applications), Mainframe Points, BPM Points, BI Points, Service Points, etc.