“…2.2.1. Categorical model In the categorical model (Willis & Houston, 1990;Zhu, 2008;Venugopalan, Sarath, Pillai, Krishnan, & Anbuudayasankar, 2014), suppliers are evaluated by criteria such as cost, quality, speed of delivery, etc. With regard to each criterion, suppliers are classified as good, fair, poor and assigned a (þ), (0) or (À) for each level, respectively.…”