Logistic Regression: A Self-learning Text, Third Edition (Statistics in the Health Sciences)

7. State the logit form of a logistic model that treats
   region as a polytomous exposure variable and controls
   for the confounding effects of AGE, SMK, RACE, and
   SEX. (Assume no interaction involving any covariates
   with exposure.)


8. For the model of Exercise 7, give an expression for the
   odds ratio for theE, Drelationship that compares
   urban with rural persons, controlling for the four
   covariates.


9. Revise your model of Exercise 7 to allow effect modi-
   fication of each covariate with the exposure variable.
   State the logit form of this revised model.


10. For the model of Exercise 9, give an expression for the
    odds ratio for theE, Drelationship that compares
    urban with rural persons, controlling for the con-
    founding and effect-modifying effects of the four
    covariates.


11. Given the model

logit PðÞ¼X aþb 1 ðÞþSMK b 1 ðÞþASB g 1 ðÞAGE

þd 1 ðÞþSMKAGE d 2 ðÞASBAGE;

where SMK is a (0, 1) variable for smoking status, ASB is a

(0, 1) variable for asbestos exposure status, and AGE is

treated continuously,

Circle the (one) correct choice among the following
statements:

a. The odds ratio that compares a smoker exposed to
asbestos to a nonsmoker not exposed to asbestos,
controlling for age, is given by exp(b 1 þb 2 þd 1 þd 2 ).

b. The odds ratio that compares a nonsmoker exposed to
asbestos to a nonsmoker unexposed to asbestos,
controlling for age, is given by exp[b 2 þd 2 (AGE)].

c. The odds ratio that compares a smoker exposed to
asbestos to a smoker unexposed to asbestos, controlling
for age, is given by exp[b 1 þd 1 (AGE)].

d. The odds ratio that compares a smoker exposed to
asbestos to a nonsmoker exposed to asbestos,
controlling for age, is given by exp[b 1 þd 1 (AGE)þ
d 2 (AGE)].

e. None of the above statements is correct.

Practice Exercises?Test 97