Traditional models of the cost of quality combine prevention and appraisal expenses and consider their coupled effect on failure costs. This approach conceals the real economic value of continuous process improvement and undermines its scope and objectives. In this paper we represent a modified cost function based on the revised model developed by Weheba and Elshennawy [1]. The modified function can be used to estimate the total reactive costs at a given stable level of operation utilizing attribute data. A case study is presented with numerical evaluations to illustrate its performance.