ORIGINAL ARTICLE Multiple criteria group decision-making for supplier selection based on COPRAS method with interval type-2 fuzzy sets Mehdi Keshavarz Ghorabaee & Maghsoud Amiri & Jamshid Salehi Sadaghiani & Golnoosh Hassani Goodarzi Received: 19 February 2014 /Accepted: 3 July 2014 /Published online: 13 August 2014 # Springer-Verlag London 2014 Abstract Supplier selection is one of the most critical activ- ities of purchasing management in a supply chain because of the key role of supplier’ s performance in achieving the objec- tives of a supply chain. Supplier selection problem requires a trade-off between multiple criteria exhibiting vagueness and imprecision with the involvement of a group of experts. This paper presents a multiple criteria group decision-making ap- proach for supplier selection problem in the context of interval type-2 fuzzy sets. A new method for ranking interval type-2 fuzzy numbers, based on the centroid of fuzzy sets, is pro- posed and compared with some methods. The proposed rank- ing method is used for extending complex proportional as- sessment (COPRAS) method for group decision-making with interval type-2 fuzzy numbers. The developed method uses a stepwise procedure for ranking and evaluating the alterna- tives, in terms of significance and utility degree, and selects the best solution considering both the positive-ideal and the negative-ideal solutions. To demonstrate the applicability of the proposed approach in supplier selection problems, an illustrative example is presented and the results are analyzed. Keywords COPRAS method . Interval type-2 fuzzy sets . Multiple criteria group decision-making . Supplier selection 1 Introduction In the past decades, supply chain management (SCM) and supplier selection problem have greatly been considered by researchers in the business management literature and prac- tice [1–8]. Supply chain management (SCM) encompasses the management of participants’ transactions in a supply chain for maximization of total supply chain profitability. SCM focuses on minimization of overall costs of the supply chain from side to side and maximization of the revenue earned from the customer in association with organization partners. Companies within a supply chain can reach the stability in competitive advantages through expanding much closer connections with all corporations. They can meaningfully decrease time and costs based on the suitable management of the supply chain as well [9]. In most situa- tions, SCM appears from several companies that have made their own supply chain. They have to work with more capable partners to reach a competitive chain. Manufac- turers must prefer more cooperative ones among a variety of available suppliers which are competent to develop long- period relationships [10]. Hence, one of the most essential activities of firms is supplier selection. Selecting suitable suppliers can significantly increase the organization com- petitiveness by decreasing the purchasing costs [11]. We can classify the supplier selection problems in the multiple criteria problems category which include both qualitative and quantitative performance indicators. It is necessary to make a trade-off between these tangible and intangible factors, in order to select the desired suppliers [12]. Conse- quently, a purchasing manager must scrutinize the trade-off among these criteria. Multiple criteria decision-making (MCDM) techniques support the decision makers (DMs) in appraising an assortment of alternatives. Depending on the purchasing conditions, criteria have varying importance and the DMs have to weigh them [13]. M. Keshavarz Ghorabaee (*) : M. Amiri : J. Salehi Sadaghiani : G. Hassani Goodarzi Department of Industrial Management, Management and Accounting Faculty, Allame Tabataba’I University, 1489684511 Dehkadeh-ye-Olympic, Tehran, Iran e-mail: m.keshavarz_gh@yahoo.com M. Amiri e-mail: Amiri@atu.ac.ir J. Salehi Sadaghiani e-mail: j.salehi.sadaghiani@gmail.com G. Hassani Goodarzi e-mail: golnoosh.h.g@gmail.com Int J Adv Manuf Technol (2014) 75:1115–1130 DOI 10.1007/s00170-014-6142-7