Quality evaluation methods – a review

Quality is understood as a set of features that determine how a product fits to satisfy certain needs. Therefore, a set of measurements X1, X2,…, Xn characterizes each product, and also serves as information in evaluation of product's quality. Individual measurements Xi are quantitative (numerical) or qualitative (non-numerical) variables expressing the value of the ith index of quality. Evaluation of the overall level of quality, comparison of similar products, measuring and reporting quality improvement and other related problems need construction of some integral quality index Q in which all individual measurements are taken into account. Several proposals for integral quality indices, such as differential approach, weighted means, mixed method, generalized index, algorithmic methods as KORTER, and PATTERN, and a multiplicative integral index are considered. A brief discussion of the properties of each approach is provided, Advantages and disadvantages are pointed out. Examples of how to find the product that exhibits the best fit to its multivariate quality index, and how to rate products according to their quality in a set of similar products are briefly shown.