- Software equation
In the study of software project estimation, the

**Software Equation**is a model with multiple variables based on assumptions of a specific distribution of effort throughout the entire length of a software development project. The models basis was formed through analysis of productivity data collected from over 4000 modern day software development projects.cite book|last=Pressman|first=Roger S.|authorlink=Roger S. Pressman|title=Software Engineering - A Practitioner's Approach|origdate=1982|edition=6th|publisher=McGraw-Hill|location=Newyork, NY|year=2005|isbn=0-07-285318-2|pages=662-663] The software equation was derived from thePutnam-Norden-Rayleigh Curve which can be used to show the non-linear correlation between time to complete the project and applied human effort.cite book|last=Pressman|first=Roger S.|authorlink=Roger S. Pressman|title=Software Engineering - A Practitioner's Approach|origdate=1982|edition=6th|publisher=McGraw-Hill|location=Newyork, NY|year=2005|isbn=0-07-285318-2|pages=679]**Model Form**The estimation model can be described in the following form.

:$E=left\; lbrack\; frac\{LOC\; x\; B^\{.333\{P\}\; ight\; brack^3\; left\; (\; frac\{1\}\{t^4\}\; ight\; )$

where

*E=Project effort measured in person-months or person-years

*LOC=a Lines of Code estimate for the project

*t=Length of project measured in months or years

*B=a "special skills factor"

*P=a "Productivity Parameter"**Defining B**B, the special skills factor, is related to the size of the product.Citeweb|url=http://www.sju.edu/~jhodgson/se/compeq.html|title=The Computational Software Equation|accessdate=2007-09-06]

**Defining P**Research from the collected productivity data supplies initial values for variable P determined by the type of software being developed. Some examples are listed below. These numbers to not apply in all situations and P can often be calculated from previous metrics information.

**ee also***

Putnam-Norden-Rayleigh Curve **References**

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