Interval-Valued Pythagorean Fuzzy QFD Design Weighted by Best-Worst Method: An Application to E-Scooter Design
Pub. online: 5 January 2026
Type: Research Article
Open Access
Open Access
Received
1 March 2025
1 March 2025
Accepted
1 December 2025
1 December 2025
Published
5 January 2026
5 January 2026
Abstract
Quality Function Deployment (QFD) is a technique used to collect Customer Requirements (CRs) for the product to be designed before the start of the manufacturing processes, and also used to determine whether CRs will be met with correlated or uncorrelated Design Requirements (DRs). In QFD technique, customers tend to explain their expectations from the product by using linguistic expressions instead of using exact numbers. Vagueness and impreciseness in linguistic expressions can be captured perfectly using fuzzy set theory. Pythagorean fuzzy (PF) sets as one of the extensions of ordinary fuzzy sets offer the decision maker a larger membership and non-membership assignment region than ordinary intuitionistic fuzzy sets. In this paper, customer requirements in QFD analysis are prioritized by Best-Worst Method (BWM), which has become a very popular optimization-based weighting method in recent years. In the proposed BWM and QFD methodology, interval-valued Pythagorean fuzzy (IVPF) sets are used for the first time in order to handle the uncertainties in the linguistic judgments. In the application, the two-phase IVPF methodology is proposed to a real life e-scooter design problem addressing 12 customer & 12 design requirements. The proposed PF methodology could determine the weights of customer requirements, and identify which of the design requirements is stronger, and make a competitive analysis to reveal the position of our company in the market under fuzzy environment. Besides, the sensitivity and comparative analyses have demonstrated the dominance of our company over the other competitors.
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Biographies
Otay İrem
İ. Otay has been working for Department of Industrial Engineering in Istanbul Bilgi University since 2019 and head of the department since 2024. She pursued a BS degree in industrial engineering at Yildiz Technical University in 2006, an MBA degree at Bahcesehir University in 2009, and a PhD degree in management engineering at Istanbul Technical University in 2015. She worked at University of California Davis (UC Davis) on a research project for almost a year as a Visiting Scholar. The name of the project is “Modelling Humanitarian Logistics Resource Allocation Problem during the Post-disaster Considering Uncertainty”. Her main research areas are the fuzzy sets and their applications, multi-criteria decision making, and mathematical programming. She gives lectures on operations research, production planning and productivity management at the undergraduate and graduate levels. Her works have been published in international journals and conference proceedings. She also edited an international book from Springer. According to Google Scholar, she has more than 1340 citations, has an h-index of 18, and an i-10 index of 27.
Kahraman Cengiz
C. Kahraman was born in Üsküdar in 1965. He started his higher education at Istanbul Technical University, Department of Industrial Engineering in 1983. He started working as a research assistant in this department, where he graduated in 1988. He received his undergraduate degree in Industrial Engineering from ITU in 1988, his master’s degree in industrial engineering in 1990, and his doctorate degree in industrial engineering in 1996. Prof. Kahraman received the title of assistant professor in 1996, associate professor in 1998, and professor in 2003 from Istanbul Technical University. Prof. Dr. Cengiz Kahraman’s main research areas include engineering economics, quality management, multi-criteria decision making, statistical decision making and fuzzy decision making. Prof. Kahraman has authored more than 300 internationally indexed articles, more than 230 international conference papers, and more than 100 international book chapters. He edited 25 international books and guest-edited special issues of many international magazines. He currently sits on the editorial boards of 20 international journals, including one as editor-in-chief. Cengiz Kahraman, who chair many international scientific conferences such as INFUS coferences, also served as the Vice Dean of ITU Faculty of Business Administration between 2004–2007 and as the Head of ITU Industrial Engineering Department between 2007–2010, and Rector Advisor between 2022–2024.
