Recently, the extensive applications of thin-film transistor liquid crystal display (TFT-LCD) products have been increasing rapidly (for example, smart phones, monitors, and liquid crystal display televisions). Supplier selection in TFT-LCD manufacturing industries has become more essential and has received considerable attention. It is a problem of comparing two suppliers and selecting the one that has a significantly higher process capability. In this paper, we consider an effective test to determine supplier selection for glass substrate processes with multiple characteristics using the yield index S pk T , which can provide an exact measure of the process yield. In order to determine the selection decisions, critical values of the hypothesis testing for two procedures are calculated. For the practitioners’ convenience in applying our procedures, various sample sizes required for designated selection powers are tabulated and discussed. For illustration purposes, a real-world problem in TFT-LCD factories is considered and solved for supplier selection evaluation.