As the survey data are both clustered and weighted, the design-based Taylor series linearization method implemented in the SUDAAN software system (Research Triangle Institute, 2002) was used to estimate standard errors of prevalence estimates and 95% confidence intervals of ORs. Significance of predictor sets was evaluated using Wald χ2 tests based on design-based variance-covariance matrices. Statistical significance was consistently evaluated using .05-level two-sided tests.
