The oldest metric for software quality economic study is that of “cost per defect.” While there may be earlier uses, the metric was certainly used within IBM by the late 1960′s for software; and probably as early as 1950′s for hardware.
For software the cost-per-defect-metric has developed into an urban legend, with hundreds of assertions in the literature that early defect detection and removal is cheaper than late defect detection and removal by more than 100 to 1. This is true mathematically, but there is an economic problem with the cost per defect calculations that will be discussed in the article.
As will be shown, cost per defect is always cheapest where the greatest volumes of defects are found. More importantly the cost-per-defect metric tends to ignore the major economic value of improved quality: shorter development schedules and reduced development costs outside of explicit defect repairs.
Read the full PDF here: http://namcookanalytics.com/wp-content/uploads/2013/07/COST-PER-DEFECT-2013.pdf