18.4 Summary of Techniques for Estimating Size

This chapter and other chapters in this book have presented numerous techniques for estimating size, including several techniques that can produce a size estimate in lines of code. Table 18-5 summarizes the techniques that have been presented so far.

Table 18-5: Techniques for Estimating Size
Technique	Chapter	Kind of Size That Can Be Estimated
Analogy	11	features, function points, Web pages, GUI components, database tables, interface definitions, lines of code
Decomposition	10	features, function points, Web pages, GUI components, database tables, interface definitions, lines of code
Dutch Method	18	function points, lines of code
Estimation Tools	14	function points, lines of code
Function Points	18	function points, lines of code
Fuzzy Logic	12	function points, lines of code
Group Reviews	13	features, user stories, story points, requirements, use cases, function points, Web pages, GUI components, database tables, interface definitions, classes, functions/subroutines, lines of code
GUI Elements	18	function points, lines of code
Standard Components	12	function points, lines of code
Story Points	12	story points, lines of code
Wideband Delphi	13	features, user stories, story points, requirements, use cases, function points, Web pages, GUI components, database tables, interface definitions, classes, functions/subroutines, lines of code

The entries in the table's "Kind of Size That Can be Estimated" column really depend on the calibration data you have. The most common kinds of size data—and the most generally usable—are function points and lines of code.

As Chapter 15, "Use of Multiple Approaches," discussed, the best estimators usually use multiple estimation techniques and then look for convergence or spread among the estimates. The different approaches listed in Table 18-5 provide numerous options for estimating size in different ways and then comparing your estimates.

Tip #84

With better estimation methods, the size estimate becomes the foundation of all other estimates. The size of the system you're building is the single largest cost driver. Use multiple size-estimation techniques to make your size estimate accurate.