Taguchi Larger-the-Best Software Quality Metrics

A set of metrics (numerical software measurements) based on the Taguchi philosophy have been proposed for measuring software quality. The Taguchi approach, originally developed for manufacturing processes, defines quality in terms of "loss imparted to society" by a product after delivery of the product to the end user. The nominal-the-best and smaller-the- best loss functions developed by Taguchi have been adapted for software products and case studies have been presented to illustrate the adaptation. This paper adapts the Taguchi larger-the-best loss function to software quality metrics like Mean Time Between Failure (MTBF). Software metrics like MTBF have a desired (target) value of infinity and therefore should be as large as possible. A value of infinity however is not easy to work with, and poses several challenges. An elegant solution is proposed in this paper. The solution uses the reciprocal of infinity (that is, zero) and the applicable Taguchi loss functions are modified to use reciprocal parameters.