The data for this question consist of a sample of 50 persons from the 1967-1980 Evans County
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a. Assuming a regression model that contains the main effects of CHR and AGE, as well as the interaction effect between CHR and AGE, carry out a Wald test for significant interaction. (Specify the null hypothesis, the form of the test statistic, and its distribution under the null hypothesis.) What are the conclusions about interaction based on this test?
b. For the same model considered in part (a), how would one carry out an LR test for significant interaction? (Specify the null hypothesis, the form of the test statistic, and its distribution under the null hypothesis.) What are the conclusions about interaction based on this test? How do these results compare with those in part (a)?
c. Assuming no interaction, carry out a Wald test for the significance of the CHR variable, controlling for AGE. (As in the preceding parts of this problem, state the null hypothesis, the form of the test statistic, and its distribution under the null hypothesis.) What are the conclusions based on this test?
d. For the same no-interaction model considered in part (c), how would one carry out an LR test for significance of the CHR variable, controlling for AGE? (Specify the null hypothesis, the form of the test statistic, and its distribution under the null hypothesis.) Why can't one actually carry out this test given the output information provided earlier?
e. For the no-interaction model considered in part (c), compute a 95% confidence interval for the coefficient of the CHR variable, controlling for AGE. What does the computed confidence interval say about the reliability of the point estimate of the effect of CHR in this model?
f. What is the overall conclusion about the effect of CHR on survival time based on the computer results from this study?
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Related Book For
Applied Regression Analysis And Other Multivariable Methods
ISBN: 632
5th Edition
Authors: David G. Kleinbaum, Lawrence L. Kupper, Azhar Nizam, Eli S. Rosenberg
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