$5-76.$ In $$Orthogonal Design for Process Optimization and Its Application to Plasma Etching$($Solid State Technology, May $1987),$ G$.$ Z$.$ Yin and D$.$ W$.$ Jillie describe an experiment to determine the effect of C$2$F$6$ flow rate on the uniformity of the etch on a silicon wafer used in integrated circuit manufactur$-$ ing. Three flow rates are used in the experiment, and the result$-$ ing uniformity $($in percent$)$ for six replicates is shown here