“…When a new product is being developed, it is not normally possible to elicit explicit data because of the implicit nature of early-stage product conceptualisation (Yan et al 2006). Since Zadeh (1965) introduced fuzzy set theory, and Bellman and Zadeh (1970) described the decision-making method in fuzzy environments, an increasing number of manufacturing studies have dealt with fuzzy-logic-based decisionmaking models for new product development (Bu¨yu¨-ko¨zkan and Feyzio glu 2004, Mikhailov and Tsvetinov 2004, Feyzio glu and Bu¨yu¨ko¨zkan 2008, Zhang and Chu 2009, Chiang and Che 2010 and cooperative games where the knowledge about the worth of coalitions is described by fuzzy intervals (Nishizaki and Sakawa 2000, Mares 2001, Tsurumi et al 2001, Espin et al 2007, Al-Ahmari 2008, Jing and Lu 2010, Mallozzi et al 2011. According to Zadeh (1975), it is very difficult for conventional quantification to reasonably express complex situations and it is necessary to use linguistic variables whose values are words or sentences in a natural or artificial language.…”