The Importance of the Place of Defuzzification Step In Fuzzy Multi Criteria Decision Making

Fuzzy logic and fuzzy based techniques are applied constantly in both social sciences and engineering sciences for fuzzy systems. However, theoretical content is neglected occasionally in these developed methods. Even sometimes, propositions and applications are developed by using fuzzy numbers ignoring theoretical contents. In some cases, there are lots of different fuzzy solution propositions of same crisp method. Because of these, despite applying similar methods to same data set, very different results can be obtained. Fuzzy multi criteria decision making method propositions are evaluated by using simulation technique in this study to explore and compare the results of fuzzy applications. Simulation applications are applied to AHP, TOPSIS, VIKOR and MOORA methods which are the most common multi criteria decision making methods as both crisp and fuzzy in the literature. Obtained results are evaluated and interpreted for both selection of the best alternative and ranking of all alternatives. All obtained results of simulation applications show that defuzzified results are significantly different than each other for each multi criteria decision making method and each different defuzzification step.