Defect Removal Rates

As has been stated previously, Agile encompasses more than a methodology or framework. Total Quality Management is also of major importance because higher quality = less rework = higher thoughput into production. The following table highlights the defect removal efficiency rates associated with the most common techniques. For a relatively modest input -e.g. formal code inspection, the output is a much lower defect density. The interesting thing is the fact that Testing is less effective at finding defects than formal activities. Which one is the cheapest to perform?
 

Removal Step	Lowest Rate	Modal Rate	Highest Rate
Informal design reviews	25%	35%	40%
Formal design inspection	45%	55%	65%
Informal code reviews	20%	25%	35%
Formal code inspections	45%	60%	70%
Modeling or prototyping	35%	65%	80%
Personal desk checking of code	20%	40%	60%
Unit Test	15%	30%	50%
New Function (component Test)	20%	30%	35%
Integration Test	25%	35%	40%
Regression Test	15%	25%	30%
System Test	25%	40%	55%
Low-Volume beta Test ( < 10 sites)	25%	35%	40%
High-Volume beta test *> 1000 sites)	60%	75%	85%

Please refer to Software Estimation - demystifying the black Art by Steve McConnell.