Evaluating the quality level of a product with multiple quality characterisitcs

Most of the studies of quality systems or product assessment deal with a single quality characteristic to determine the quality loss. From the customer's point of view, however, products are often judged by more than one quality characteristic. For this reason, a multivariate quality loss function is required as an extension to the Taguchi loss function to capture the overall losses caused by bad quality when multiple quality characteristics are present. A numerical example is illustrated showing that using inappropriate univariate loss functions will give an underestimated quality loss or even ignored the loss incurred because of the poor quality.