What can fuzziness do for capability analysis based on fuzzy data

One advantage of process incapability index over the classical process capability index is that it provides uncontaminated separation between process accuracy and process precision. However, the value of the index is dicult to determine accurately when process parameters cannot be determined precisely. In such a case, fuzzy set theory can be applied to obtain more exible and sensitive information. In this paper, a fuzzy process incapability index is proposed when the specication limits are assumed to be type- 2 fuzzy. When the process mean and variance are unknown and when the observations are measured imprecisely, three fuzzy estimators are considered. A simulation study is conducted based on the Thin-Film-Transistor Liquid-Crystal Display (TFT-LCD) fuzzy process. By applying the total integral value method to the membership function of a fuzzy index, it becomes easier to make a comparison of the quality of dierent processes.