Modeling relationships between two categorical variables when data are missing: Examining consequences of the missing data mechanism in an HIV data set

Analysts evaluating the strengths of relationships between variables in behavioral science research must often contend with the problem of missing data. Analyses are typically performed using data for cases that are either complete in all the variables, or assume that the data are missing at random. Often, these approaches yield biased results. Using empirical data, the current work explores the implications and consequences of using various statistical models to describe the association of two variables, one ordinal and one dichotomous, in which data are incomplete for the dichotomous variable. These models explicitly reflect the missing data mechanism; models that hypothesize nonignorable nonresponse are given particular attention. Both the statistical fit and substantive consequences of these models are examined. This new methodological approach to examining nonignorable nonresponse can be applied to many behavioral science data sets containing an ordinal variable.