In this chapter, the author applies a real-life gold-plating case study to illustrate the robustness optimization procedure using an $L18(2137)$ orthogonal array, measured raw data, and S/N (signal-to-noise) ratios of three static characteristics (nominal-the-best, larger-the-better, and smaller-the-better). Additionally, a two-step optimization procedure for a nominal-the-best type characteristic and a procedure for categorical output responses (such as appearance judgment based on visual inspection) are discussed.