Deriving an Overall Evaluation Index with Multiple CTQs in Six Sigma Management

Evaluation indices for products or services are important to improve the internal process of the company and to compare those with competitive ones. The sigma level in Six Sigma management does important role to evaluate the core characteristic, CTQ(Critical To Quality), derived in the considered product/service or process. In this research, we propose an overall evaluation index for the product/service or process with multiple characteristics, in other words, multiple CTQs. The proposed overall evaluation index is useful for the cases that the single CTQ is not enough to evaluate the practical interests, for example, the final products and services with complex procedures and relatively large scaled processes. This approach is discussed with sigma level for applying Six Sigma Projects, however, it is applicable to indices based on proportion or percentage as well. The practical examples with a manufacturing process and a customer survey based on focus group interview are given for illustrations.