Quality Loss Function – A Common Methodology for Three Cases

The quality loss function developed by genichi taguchi considers three cases, nominal-thebest,smaller-the-better, and larger-the-better. the methodology used to deal with the larger-thebettercase is slightly different than the other two cases. this research employs a term calledtarget-mean ratio to propose a common formula for all three cases to bring about similarityamong them. the target-mean ratio can take different values representing all three cases tobring consistency and simplicity in the model. in addition, it eliminates the assumption of targetperformance at an infinite level and brings the model closer to reality. characteristics such asefficiency, coefficient of performance, and percent non-defective are presently not larger-thebettercharacteristics due to the assumption of target performance at infinity and the subsequentnecessary derivation of the formulae. these characteristics can also be brought under thecategory of the larger-the-better characteristics. an example of the efficiency of prime moversis discussed to illustrate that the efficiency can also be considered as a larger-the-bettercharacteristic. a second example is presented to suggest the subtle differences between bothmethodologies.