m.h Haghighi - Department oflndustrial Engineering, Faculty ofEngineering, Shahed University, Tehran, Iran
s.m Mousavi - Department oflndustrial Engineering, Faculty ofEngineering, Shahed University, Tehran, Iran
v Mohagheghi - Department oflndustrial Engineering, Faculty ofEngineering, Shahed University, Tehran, Iran

Fuzzy multiple criteria decision making is one of the most widely used decision methodologies in engineering, technology, science and management and business. In recent years, because of increasing the accuracy and breadth of the opinions, attention to group decision making has increased; so, it is necessary to determine the importance of each decision maker in this process. In this paper, concepts of the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) is developed for determining weights of decision makers under group decision environments, in which each individual decision information is expressed by a matrix in interval type—2 fuzzy numbers. In this paper the positive and negative ideal solutions of group decision are defined and are expressed by a matrix, respectively. Finally, for the validation of the method, a numerical example of the previous studies has been presented.

Multiple attributes group decision making (MAGDM); Weights of decision makers; TOPSIS; Interval type—2 fuzzy sets (IT2FSs)