Sample size: achieving quality and reducing financial loss

Determining the proper sample size such that quality is assured while financial losses are not unnecessarily incurred is critical to an effective quality program. The main purpose of the present work is to design a fuzzy controller to adjust sample sizes according to potential fuzzy loss penalties. A set of fuzzy rules is given where, depending on the antecedents, the sample size may be decreased, moderately modified, or increased. At any given moment the proportion of defects in the sample determines the firing strength of the rules suggesting an appropriate sample size. These rules are then modified to include an analysis of the decision maker’s belief that in a particular situation an inappropriate rule is being considered such that an expected loss would be incurred in meeting or falling short of defined quality goals.