correlations are all similar, this would suggest that an
exchangeable structure is reasonable.
- Estimated OR¼exp(0.3601)¼1.43.
95% CI: exp[0.36011.96(0.8122)]¼(0.29, 7.04).
- Consistency is an asymptotic property. As the number
of clusters approaches infinity, the odds ratio estimate
should approach the true odds ratio even if the corre-
lation structure is misspecified. However, with a finite
sample, the parameter estimate may still differ from
the true parameter value. The fact that the parameter
estimate for DIARRHEA is so sensitive to the choice of
the working correlation structure demonstrates a
degree of model instability.
- No, because the Wald test statistic is a function of
both the parameter estimate and its variance. Since
the variance is typically affected by the choice of cor-
relation structure, the Wald test statistic would also be
affected.
Answers to Practice Exercises 565
