(Solution) - In Exercise 12 28 we have the following data concerning wear -(2025 Original AI-Free Solution)

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In Exercise- 12.28, we have the following data concerning wear of a bearing:

(a) The following model may be considered to describe this data:
yi = 00 + ?1xl, + ?2X2i + ?12x1ix2i + ?i,
for i = 1,2,...,6. The x1x2 is an "interaction"' term. Fit this model and estimate the parameters.
(b) Use the models (x), (x1, x2), (x2). (x1, x2, x1x2) and compute PRESS, Cp, and s" to determine the 'best'' model.