Covariate

A covariate is a continuous variable that is expected to change (“vary”) with (“co”) the outcome variable of a study. Generally speaking, a covariate can refer to any continuous variable that is [Page 283]expected to correlate with the outcome variable of interest. Although the term is sometimes used in this way, it is typically used to refer to variables that are not of direct or substantive interest in the study. Because they are associated with the outcome variable but are not the focus of the study, covariates are often called “extraneous” or “nuisance” variables. They are included in the analysis to increase precision or rule out alternative explanations for the findings, but they are not the focus of the analysis.

Accounting, or controlling, ...