Chapter 12.10, Problem 12.115ACI

Diet of ducks bred for broiling. Corn is high in starch content; consequently, it is considered excellent feed for domestic chickens. Does corn possess the same potential in feeding ducks bred for broiling? This was the subject of research published in Animal Feed Science and Technology (April 201 0). The objective of the study was to establish a prediction model for the true metabolizable energy (TME) of corn regurgitated from ducks. The researchers considered 11 potential predictors of TME: dry matter (DM), crude protein (CP), ether extract (EE), ash (ASH), crude fiber (CF). neutral detergent fiber (NDF), acid detergent fiber (ADF), gross energy (GE), amylose (AM), amylopectin (AP), and amylopectin/amylose (AMAP). Stepwise regression was used to find the best subset of predictors. The final stepwise model yielded the following results:

     $\widehat{TME}=7.70+2.14\left(\text{AMAP}\right)+.16\left(\text{NDF}\right),{\mathrm{R}}^2=.988,s=.07,GlobalFp-value=.001$

1. a. Determine the number of 1-tests performed in step 1 of the stepwise regression.
2. b. Determine the number of 1-tests performed in step 2 of the stepwise regression
3. c. Give a full interpretation of the final stepwise model regression results.
4. d. Explain why it is dangerous to use the final stepwise model as the "best" model for predicting TME.
5. e. Using the independent variables selected by the stepwise routine, write a complete second-order model for TME.
6. f. Refer to part e. How would you determine if the terms in the model that allow for curvature are statistically useful for predicting TME?