# Question: Refer to the feed efficiency data in Exercise 12 14 The

Refer to the feed efficiency data in Exercise 12.14. The researcher is relating y, feed efficiency, to the explanatory variables: x1, amount of feed additive; and x2, amount of copper placed in the feed. Consider the following models:

Model 1: y = β0 + β1x1 + ɛ

Model 2: y = β0 + β1x1 + β2x2 + ɛ

Model 3: y = β0 + β1x1 + β2x21 + β3x2 + ɛ

Model 4: y = β0 + β1x1 + β2x21 + β3x2 + + β4x1x2 + β5x21x2 ɛ

a. In model 4, which of the coefficients are significantly different from 0 at the .05 level?

b. Do the added terms in model 4 provide a significant gain over model 3 in the fit of the model.

c. Are your conclusions from parts (a) and (b) consistent? Explain in detail.

Model 1: y = β0 + β1x1 + ɛ

Model 2: y = β0 + β1x1 + β2x2 + ɛ

Model 3: y = β0 + β1x1 + β2x21 + β3x2 + ɛ

Model 4: y = β0 + β1x1 + β2x21 + β3x2 + + β4x1x2 + β5x21x2 ɛ

a. In model 4, which of the coefficients are significantly different from 0 at the .05 level?

b. Do the added terms in model 4 provide a significant gain over model 3 in the fit of the model.

c. Are your conclusions from parts (a) and (b) consistent? Explain in detail.

## Answer to relevant Questions

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