what is meant by the statement that the test result
depends on the coding of the variable HT. Should
such a test be carried out? Explain briefly.- Suppose for the model described in Exercise 3 that a
Wald test is carried out for the significance of the two-
factor product term HTAGE. Is this test dependent
on coding? Explain briefly. - Suppose for the model described in Exercise 3 that a
Wald test is carried out for the significance of the main
effect term AGE. Why is this test inappropriate here? - Using the model of Exercise 3, describe briefly the
hierarchical backward elimination procedure for
determining the best model. - Suppose the interaction assessment stage for the
model of Example 3 finds the following two-factor
product terms to be significant: HTCT and HT
SEX; the other two-factor product terms are not
significant and are removed from the model. Using
the hierarchy principle, what variables must be
retained in all further models considered. Can these
(latter) variables be tested for significance? Explain
briefly. - Based on the results in Exercise 9, state the (reduced)
model that is left at the end of the interaction
assessment stage.
Test True or False? (Circle T or F)
T F 1. The three stages of the modeling strategy
described in this chapter are interaction assess-
ment, confounding assessment, and precision
assessment.
T F 2. The assessment of interaction should precede
the assessment of confounding.
T F 3. The assessment of interaction may involve
statistical testing.
T F 4. The assessment of confounding may involve
statistical testing.
T F 5. Getting a precise estimate takes precedence
over getting an unbiased answer.
T F 6. During variable specification, the potential
confounders should be chosen based on
analysis of the data under study.
T F 7. During variable specification, the potential
effect modifiers should be chosen by consider-
ing prior research or theory about the risk
factors measured in the study.
T F 8. During variable specification, the potential
effect modifiers should be chosen by198 6. Modeling Strategy Guidelines