Modeling the Cost of Software Quality

This paper offers an extrapolation of the manufacturing and service industries' Cost of Quality Model to the business of software development. The intent is to provide a theoretical account of the changing quality cost structure as a function of a maturing software development process. Thus, the trends in expenditures due to the four major quality cost categories --appraisal, prevention, internal failures, and external failures --are presented over the five levels of software process maturity, according to the Software Engineering Institute's (SEI's) Capability Maturity Model for Software (CMM). The Software Cost of Quality Model conservatively proposes that the total cost of quality, expressed as a percentage of the cost of development, can be decreased by approximately two-thirds as process maturity grows from Level 1 to Level 5 of the SEI's CMM.