The Taguchi Quality Loss Function

The quality loss is crucial in Taguchi s theory. It is based on the assumption that when a functional characteristic y deviates from the specified target value m, the customer and the society in general experiences an economical loss due to poorer product quality. This economic loss is expressed as the loss function L(y). Based on this, Taguchi defines the quality loss for not being on target by means of the quadratic quality loss function (Phadke (1989), Taguchi (1986))  

With the substitution of Equation (9.2) into Equation (9.1) it is able to calculate the quality loss for a given value of y. More on the determination of k can be found in (Phadke (1989)). 

The ratio takes into account the mean and the variance of the test results, and is as a rule of thumb always maximised. This leads to several specialised S/N ratios, depending on the nature of the comparison variable. There are three basic S/N ratios, but according to (Fowlkes and Creveling (1995)), the variety of S/N ratios is limitless. The three possible categories of quality characteristics or most widely used S/N ratios are  

The conversion to the signal-to-noise ratio can be viewed as a scale transformation for convenience of better manipulation. It offers an objective way to look at two characteristics, namely, variation and mean value. Analysis using the signal-to-noise ratio has two main advantages  

For the robust design of a product, the following two steps are required  

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