Software Defects - Do Late Bugs Really Cost More?

ecklesweb asks: "Do software defects found in later phases of the software development cycle REALLY cost THAT much more than defects found in earlier phases? Does anyone have any empirical data (not anecdotal) to suggest that this logarithmically increasing cost idea is really true? That is the question I use whenever I want to tick off a trainer. Seriously, though, it seems an important question given the way this 'concept' (or is it a myth?) drives the software development process."

"If you're a software engineer, one of the concepts you've probably had driven into your head by the corporate trainers is that software defects cost logarithmically more to fix the later they are found in the software development life cycle (SDLC).

For example, if a defect is found in the requirements phase, it may cost $1 to fix. It is proffered that the same defect will cost $10 if found in design, $100 during coding, $1000 during testing.

All of this, to my knowledge, started by Barry Boehm in papers[1]. In these papers, Mr. Boehm indicates that defects found 'in the field' cost 50-200 times as much to correct as those corrected earlier.

That was 15 years ago, and as recently as 2001 Barry Boehm indicates that, at least for small non-critical systems, the ratio is more like 5:1 than 100:1[2].

[1] - Boehm, Barry W. and Philip N. Papaccio. 'Understanding and Controlling Software Costs,' IEEE Transactions on Software Engineering, v. 14, no. 10, October 1988, pp. 1462-1477

[2] - (Beohm, Barry and Victor R. Basili. 'Software Defect Reduction Top 10 List,' Computer, v. 34, no. 1, January 2001, pp 135-137.)"

Always remember the 90-90 rule.

[TheSHAD0W]

The rule is, 90% of the bugs take up 90% of your budget, and the remaining 10% take up the other 90% of your budget. This goes the same for time before deadline.

Re:Thigs they don't tell you ...

[penguin7of9]

The bugs might be cheaper to fix, but they cost a lot more to find.

Not if you are a company like Microsoft or Sun and you let your customers do your bug hunting for you, for free.

Of course, that's also how bug hunting works for open source software, but with OSS, at least I don't pay anybody for the privilege of finding their bugs for them.

Re:Thigs they don't tell you ...

[cookiepus]

(*)Just F*cking Do It

it's called 'Incremental Development' :)