2 Taguchi believes that the customer becomes increasingly dissatisfied as performance departs farther away from the target. He suggests a quadratic curve to represent a customer's dissatisfaction with a product's performance. The quadratic curve is the first term when the first derivative of a Taylor Series expansion about the target is set equal to zero. The curve is centered on the target value, which provides the best performance in the eyes of the customer. Identifying the best value is not an easy task.
Targets are sometimes the designer's best guess.
LCT represents lower consumer tolerance and UCT represents upper consumer tolerance. This is a customer- driven design rather than an engineers specification. Your organization's particular circumstance will shape how you define consumer tolerance for a product. Calculating the average loss permits a design team to consider the cost benefit analysis of alternate designs with different costs yielding different average losses. As seen in figure 2, there is some financial loss incurred at the upper consumer tolerance.