20.3 Good BenefitCost Ratio


18.1 Software Inspection Process

Let's use our total life cycle cost model to determine the cost of developing 10,000 lines of code using software testing. The formula is software size multiplied by 10.51, less the test hours times nine. Our total life cycle cost for using software testing alone is 45,100 hours.

Let's use our productivity model to determine the old productivity of using testing. The formula is software size divided by the total life cycle costs of testing. Divide 10,000 by 45,100, and the old productivity of testing is 0.22.

Let's use our total life cycle cost model to determine the cost of developing 10,000 lines of code using inspections. The formula is software size multiplied by 10.51, less the inspection hours times 99 and less the test hours times 9. Our total life cycle cost for using the Software Inspection Process is 17,425 hours.

Let's use our productivity model to determine the new productivity of using the Software Inspection Process. The formula is software size divided by the total life cycle costs of the Software Inspection Process. Divide 10,000 by 17,425, and the new productivity of the Software Inspection Process is 0.57.

Let's determine the difference between the old productivity of software testing and the new productivity of inspections. The formula is old productivity of software testing divided by new productivity of the Software Inspection Process. Divide 0.22 by 0.57. The difference between the old productivity of testing and the new productivity of the Software Inspection Process is 0.39.

The special, new, or additional costs that are required to introduce inspections consist of the training and inspection costs. The training costs to prepare four people to use inspections to help produce 10,000 lines of code are $11,240. The inspection cost for our four trained inspectors to evaluate 10,000 lines of code is $70,833. This amounts to nearly 42 Software Inspection Process runs. That totals $82,073 to introduce the Software Inspection Process as a SPI method. Table 32 illustrates the breakeven point of the Software Inspection Process.

Table 32: Breakeven Point of Software Inspection Process

SPI Method

Benefits/Costs

Software Size

10,000

Total Life Cycle Cost Hours (Testing)

45,100

Old Productivity (Testing)

0.22

Total Life Cycle Cost (Inspection)

17,425

New Productivity (Inspection)

0.57

Productivity Difference (Testing/Inspection)

0.39

Special Costs (Inspection)

$82,073

Breakeven Point (Inspection)

$133,751

Breakeven Point After Project Start (Inspection)

129 Hours

Now we are ready to determine the breakeven point of using the Software Inspection Process to produce 10,000 lines of code. Divide the special costs of $82,073 by one less the productivity difference of 0.39. The breakeven point of using the Software Inspection Process to help produce 10,000 lines of code is $133,751.

Finally, let's put the breakeven point of the Software Inspection Process into proper perspective. Subtract the special costs of $82,073 from the breakeven point of $133,751, and divide the results by 400. (Divide by 100, which converts dollars into hours, and then divide by 4, which converts staff hours into elapsed or calendar time). This final manipulation tells us that the special costs of $82,073 will be recovered in 129 hours after project start. This is less than one calendar month.




ROI of Software Process Improvement. Metrics for Project Managers and Software Engineers
ROI of Software Process Improvement: Metrics for Project Managers and Software Engineers
ISBN: 193215924X
EAN: 2147483647
Year: 2004
Pages: 145

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