Software Tips
Software Estimation Method Examination: Analogy
Using the analogy method for software estimation, an analyst uses reasoning that compares one program to previously completed programs.
Analogy is a method with which an estimator can crudely quantify or rationalize the difference among software projects. It is a quick and easy approach that can be used when little project information is available. Measures of analogy can include software lines of code (SLOC), code complexity, cost or schedule and can be expressed as a percentage or actual amounts. Care should be used in quantifying Complexity factors as they can be subject to opinion. Also, analysts must ask themselves to what degree are the two projects in comparison actually similar; for no two projects are truly alike.
Key questions that should help both to quantify project differences as well as to qualify project differences are:
- What code was measured?
- How was it counted?
- What code was ignored?
- Do you know what these numbers do/do not include?
Key questions that should help both to quantify project differences as well as to qualify project differences are:
Additive Example:
Old project data:
Size = 50,000 SLOC
Actual Effort = 500 person months
This equates to 100 SLOC per person month
New project data:
Old project reference size = 50,000 SLOC
Additional displays = 3,500 SLOC
Less, data management = 9,500 SLOC
Estimated size = 44,000 SLOC
Estimated effort = 44,000 SLOC / 100 SLOC per person month
Estimated effort = 440 person months effort to develop new program
Multiplicative Example:
Old project data:
Size = 50,000 SLOC
Actual effort = 500 person months
New project data:
Size = 25,000
Engineer assessment: 25% less complex
Estimated Effort = [500*(25,000/50,000)]*(1-.25)
Estimated Effort = 187.5 person months
