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Statistics 305 Final Exam December 12, 2007 Instructor: Dr. Wu Name Note: Points for each question are indicated in the left margin in squate brackets. J. The data used in creating the attached one page of regression analysis printout come from a study of a nitride etch process on a single wafer plasma etcher. The process variables studied were 2 = power applied to the cathode (W) £9 = pressure in the reaction chamber (mTorr) <3 = gap between the anode and the cathode (cm) 4 = flow of the reactant gas Cos and the response variable was y = selectivity of the process (SiN /polysilicon). Note that the “Stdirr Pred y” column on the output is for the second regression analysis. Use the first regression analysis output in answering the questions (a}—(d) below. Note that Zy = 0.9636 and S\(x3i — Fs)? = 0.3055. (a) What fraction of observed raw variation in y is explained by a linear equation in £3? 2] 2 , R= 0777 (b) What is the sample correlation between y and 23? PI ~ JR = -a99F (Same Sign aA that of 4) (c) Give a 95% upper contidence bound for the increase in mean value of selectivity of the process for a 0.2 cm increase in gap between the anode and the cathode. (No nced to simplify.) 7 s 5 PEP 8 g2(& +f Ee = 0.2 (1 086 tiBs Fe) QOD of ty % A833 {d) Give a 95% two-sided prediction interval for the next selectivity of the process when gap between the anode and the cathode equals 1.1 em. (No need to simplify.) ia $b BE a No WEE a0) 7 Yt Su Sts * Se; -3F 2.262 SE 2,529 —hOkE OD 4 2,202: 4.0967. fiber Ged POSS 
