terms of an odds ratio parameter, give the formula for
the test statistic, state the distribution of the test sta-
tistic under the null hypothesis, and, finally, carry out
the test using the above printout for Model I. Is the
test significant?
- Using the printout for Model I, compute the point
estimate and 95% confidence interval for the odds
ratio for the effect of SMK controlling for the other
variables in the model.
- Now consider Model II: Carry out the likelihood ratio
test for the effect of the product term SMKNS on
the outcome, controlling for the other variables in the
model. Make sure to state the null hypothesis in terms
of a model coefficient, give the formula for the test
statistic and its distribution and degrees of freedom
under the null hypothesis, and report theP-value. Is
the test significant?
- Carry out the Wald test for the effect of SMKNS,
controlling for the other variables in Model II. In
carrying out this test, provide the same information
as requested in Question 3. Is the test significant?
How does it compare to your results in Question 5?
- Using the output for Model II, give a formula for the
point estimate of the odds ratio for the effect of SMK
on cervical cancer status, which adjusts for the con-
founding effects of NS and AS and allows for the
interaction of NS with SMK.
- Use the formula for the adjusted odds ratio in Ques-
tion 7 to compute numerical values for the estimated
odds ratios when NS¼1 and when NS¼0.
- Give a formula for the 95% confidence interval for the
adjusted odds ratio described in Question 8 (when
NS¼1). In stating this formula, make sure to give an
expression for the estimated variance portion of the
formula in terms of variances and covariances
obtained from the variance–covariance matrix.
- Use your answer to Question 9 and the estimated
variance–covariance matrix to carry out the computa-
tion of the 95% confidence interval described in Ques-
tion 7.
- Based on your answers to the above questions, which
model, point estimate, and confidence interval for the
effect of SMK on cervical cancer status are more
appropriate, those computed for Model I or those
computed for Model II? Explain.
Test 161
