Multilevel modelling for measuring interaction of effects between multiple categorical variables : An illustrative application using risk factors for preeclampsia
Background: Measuring multiple and higher-order interaction effects between multiple categorical variables proves challenging. Objectives: To illustrate a multilevel modelling approach to studying complex interactions. Methods: We apply a two-level random-intercept linear regression to a binary outcome for individuals (level-1) nested within strata (level-2) defined by all observed combinations of