Comparison of Integrated Multi-Criteria Decision-Making Methods Based on Interval Type-2 Fuzzy Sets

Multi-criteria decision making (MCDM) is a process of evaluating and ranking the various alternatives with respect to the criteria using subjective judgments of decision maker(s). Since the classical MCDM methods cannot deal with imprecise and uncertain information in the decision-making process, MCDM methods based on Type-1 fuzzy sets are suggested. Afterwards, Type-2 fuzzy set characterized by a fuzzy membership function was introduced as an extension to Type-1 fuzzy sets. Interval Type-2 fuzzy sets (IT2FSs) are the most widely used Type-2 fuzzy sets. Various MCDM methods based on IT2FSs have been proposed and applied on different fields. In this chapter, two integrated methods are introduced by using AHP, COPRAS, and VIKOR methods based on IT2FSs. The proposed integrated methods are carried out to evaluate life quality of 28 European Union countries and another six countries, Iceland, Macedonia, Montenegro, Serbia, Turkey, and Kosovo with respect to 30 subjective criteria.