Subgroup analysis involves subdividing respondents in a survey into groups on the basis of demographic characteristics (e.g. race, ethnicity, age, education, or gender) or other variables (e.g. party identification, health insurance status, or attitudes toward the death penalty). Analyses of subgroups can be done for a number of reasons. A researcher might analyze differences in variable means or distributions across subgroups to identify disparities or other differences. For example, a researcher studying health care insurance may want to test whether there are differences in the proportion of respondents in different income, education, or race subgroups who are covered by private health care insurance.

Researchers may also want to compare bivariate relationships or multivariate analyses across subgroups to test whether relationships between variables are moderated by subgroup ...