Taguchi Smaller-the-Best Software Quality Metrics

Taguchi-based software metrics (numerical software measurements) define software quality in terms of "loss imparted to society" after a software product is delivered to the end user. Previous work has focused on nominal-the-best and larger-the-best loss functions for estimating the loss to society. This paper focuses on the smaller-the-best loss function for estimating the loss to society. The smaller-the-best loss function is for a property whose value should be as small as possible. It is shown that the smaller-the-best loss function can be obtained from the nominal-the-best loss function by substituting zero for t, the target value in the nominal-the-best loss function. This derivation is illustrated and a case study utilizing the derivation is presented. Taguchi-based metrics are in line with six-sigma statistical quality control techniques that have been used with software products for several years. Experiences with Taguchi-based metrics have shown good correlation with existing popularly known software quality metrics.