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198 PART TWO MANAGING SOFTWARE PROJECTS

FIGURE 8.1
1000 40–1000
Relative cost of times
correcting an
error 100 15–40 30–70
Relative cost of correcting an error 10 1 time times times times
times

10

3–6

1

Reg. Design Code Dev. System Field
test test operation

A total of 7053 hours was spent inspecting 200,000 lines of code with the result that 3112
Testing is necessary, potential defects were prevented. Assuming a programmer cost of $40.00 per hour, the total
but it’s also a very cost of preventing 3112 defects was $282,120, or roughly $91.00 per defect.
expensive way to find Compare these numbers to the cost of defect removal once the product has been
errors. Spend time shipped to the customer. Suppose that there had been no inspections, but that program-
finding errors early in
the process and you mers had been extra careful and only one defect per 1000 lines of code [significantly better
may be able to than industry average] escaped into the shipped product. That would mean that 200 defects
significantly reduce would still have to be fixed in the field. At an estimated cost of $25,000 per field fix, the cost
testing and debugging would be $5 million, or approximately 18 times more expensive than the total cost of the
costs. defect prevention effort.

It is true that IBM produces software that is used by hundreds of thousands of cus-
tomers and that their costs for field fixes may be higher than those for software orga-
nizations that build custom systems. This in no way negates the results just noted.
Even if the average software organization has field fix costs that are 25 percent of
IBM’s (most have no idea what their costs are!), the cost savings associated with qual-
ity control and assurance activities are compelling.

8.2 THE QUALITY MOVEMENT

Today, senior managers at companies throughout the industrialized world recognize
that high product quality translates to cost savings and an improved bottom line.
However, this was not always the case. The quality movement began in the 1940s
with the seminal work of W. Edwards Deming [DEM86] and had its first true test in
Japan. Using Deming’s ideas as a cornerstone, the Japanese developed a systematic