(Problem 1: 25 points) The surface roughness (Ra) on a finished part is dependent on two parameters - Depth of cut (Ap)

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Problem 1 25 Points The Surface Roughness Ra On A Finished Part Is Dependent On Two Parameters Depth Of Cut Ap 1 (45.74 KiB) Viewed 23 times

(Problem 1: 25 points) The surface roughness (Ra) on a finished part is dependent on two parameters - Depth of cut (Ap) and Cutting speed (Vc). Below is a dataset on these three variables. Vc Ra (Output) Ap 0.5 50 6.89 0.9 80 4.19 1.3 110 2.55 1.7 140 2.88 2.1 170 1.97 2.5 200 1.03 1.5 125 2.51 2.3 183 1.58 Assume a following full model: R₁ = ßo + B₁Ap + B₂Vc + B3AµVc + B₁A² + B₂V² a (i) Write down the R² and R² values (ii) Write down the estimate of the standard deviation of random error € Compute the prediction at A₂ = 1.25 and Vc = 115 (iii) (iv) Perform hypothesis testing to test if ß3 = P4 = ß5 = 0. Choose α = 0.05 (Problem 2: 15 points) Perform best subset regression and identify the best model with one term (currently the full model has five terms). Use Rå values to make your conclusion. (Problem 3: 10 points) In your own words, describe stepwise regression analysis. (What it is and how it is done)