Ranking of interval type-2 fuzzy numbers based on centroid point and spread

A concept of interval type-2 fuzzy numbers is introduced in decision making analysis as this concept is capable to effectively deal with the uncertainty in the information about a decision. It considers two types of uncertainty namely inter and intra personal uncertainties, in enhancing the representation of type-1 fuzzy numbers in the literature of fuzzy sets. As interval type-2 fuzzy numbers are crucial in decision making, this paper proposes a methodology for ranking interval type-2 fuzzy numbers. This methodology consists of two parts namely the interval type-2 fuzzy numbers reduction methodology as the first part and ranking of type- 1 fuzzy numbers as the second part. In this study, established reduction methodology of interval type-2 fuzzy numbers into type-1 fuzzy numbers is extended to reduction into standardised generalised type-1 fuzzy numbers as the extension complements the capability of the methodology on dealing with both positive and negative data values. It is worth adding here that this methodology is analysed using thorough empirical comparison with some established ranking methods for consistency evaluation. This methodology is considered as a generic decision making procedure, especially when interval type-2 fuzzy numbers are applied to real decision making problems.