You can also combine categories in ordinal or categorical variables into two categories to form dichotomous variables Certain statistical procedures require the dependent variable to be dichotomous recoded into dichotomous variables known as dummy variables for statistica procedures that require independent variables to be all interval data15 29 • You can also combine categories in ordinal or categorical variables into two categories to form dichotomous variables. Certain statistical procedures require the dependent variable to be dichotomous. Categorical variables also have to be recoded into dichotomous variables known as dummy variables for statistical procedures that require independent variables to be all interval data