Question

1. Consider the following model where y denotes the tool life and xi, x2, and tz denote the cutting speed, tool type, and type of cutting oil, respectively. There are two different tool types, A and B, and there are two type of cutting oils, low-viscosity oil and medium-viscosity oil. The two categorical predictors are 1 if type A 1 f low-viscosity oil used defined as *20 if type B and c3 0 if medium-viscosity oil used (a) Interpret the regression coefficients β0, β1, β2 and As (b) Interpret the following hypothesis tests: (a) Ho : ß2-As-0, and (b) Ho : β,-0. 2. Consider the setting of the model given in problem 1, but add the first-order interaction terms, What the null hypothesis would be if we want to test (a) whether tool type has an effect on the response, (b) whether type of cutting oil has an effect on the response (c) whether the interaction terms are significant or not.

Answer 1

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