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

Answers to
Practice
Exercises

1. F: the correct odds ratio expression is exp[bþ
   d 1 (SMK)þd 2 (HPT)]


2. T


3. F: the correct odds ratio expression is exp(2b)


4. T


5. F: the correct odds ratio expression is exp[60b
   þ 60 d(AGE)]


6. T


7. logit P(X)¼aþb 1 R 1 þb 2 R 2 þg 1 AGEþg 2 SMK
   þg 3 RACEþg 4 SEX,
   whereR 1 and R 2 are dummy variables indicating
   region, e.g.,R 1 ¼(1 if urban, 0 if other) andR 2 ¼(1 if
   suburban, 0 if other).


8. When the above coding for the two dummy variables
   is used, the odds ratio that compares urban with rural
   persons is given by exp(b 1 ).
   9 : logit PðXÞ¼aþb 1 R 1 þb 2 R 2 þg 1 AGEþg 2 SMK
   þg 3 RACEþg 4 SEXþR 1 ðd 11 AGEþd 12 SMK
   þd 13 RACEþd 14 SEXÞþR 2 ðd 21 AGE
   þd 22 SMKþd 23 RACEþd 24 SEXÞ:


9. Using the coding of the answer to Question 7, the
   revised odds ratio expression that compares urban
   with rural persons is exp(b 1 þd 11 AGEþd 12 SMK
   þd 13 RACEþd 14 SEX).


10. The correct answer is b.

Answers to Practice Exercises 101