Make-or-Buy Decisions Under Proportional Intuitionistic Fuzzy Uncertainty: A CRITIC–WASPAS Framework

Abstract

In manufacturing and supply chain management, the make-or-buy problem is a fundamental strategic challenge that requires firms to decide whether a product, component, or service should be produced internally or sourced externally. This decision involves multiple, often conflicting criteria such as cost, quality, delivery reliability, technological capability, and supply risk, as well as uncertainty and vagueness in expert evaluations. To address these issues, this study develops a proportional fuzzy decision-making framework for make-or-buy analysis using Proportional Intuitionistic Fuzzy Sets (PIFS). Expert assessments are elicited through proportional relations instead of exact numerical degrees, then transformed into PIFS and processed with the CRITIC method to derive objective criterion weights. The final ranking of alternatives is obtained using the WASPAS method, which combines additive and multiplicative utility measures. A real industrial case demonstrates that the proposed CRITIC–WASPAS–PIFS approach provides stable, interpretable judgements and a generalizable decision-support model for make-or-buy and related sourcing problems.