Some methods to deal with unacceptable incomplete 2-tuple fuzzy linguistic preference relations in group decision making

In this paper, we first propose a four-way procedure to estimate missing preference values when dealing with acceptable incomplete 2-tuple fuzzy linguistic preference relations (FLPRs). The proposed revised procedure can estimate more missing elements in the first iteration and also has more advantages than the existing methods. Then, we address situations in which an expert do not provide any comparison information for a particular alternative with other alternatives, and thus provides an unacceptable incomplete 2-tuple FLPR. We propose some methods to deal with the unacceptable situations. The main idea of these methods is to set some seed values for the unknown alternative and then to complete the unacceptable incomplete 2-tuple FLPRs by the revised procedure. We also give a simple algorithm to select the best alternative for the group decision making (GDM) problem with incomplete 2-tuple FLPRs. The analysis of advantages and drawbacks for each method are also presented.