- Categorical variable
- Categorical variables contain a finite number of categories or distinct groups. Categorical data
might not have a logical order. For example, categorical predictors include
gender, material type, and payment method.
- Discrete variable
- Discrete variables are defined only on a finite set or a countably infinite set. Minitab refers
to discrete variables as numeric variables that have a countable number of
values between any two values. For example, the number of customer complaints or
the number of flaws or defects.
- Continuous variable
- Continuous variables are numeric variables that have an infinite number of values between any
two values. A continuous variable can be numeric or date/time. For example, the
length of a part or the date and time a payment is received.
If you have a discrete variable and you want to include it in a Regression or ANOVA model, you can decide whether to treat it as a continuous predictor (covariate) or categorical predictor (factor). If the discrete variable has many levels, then it may be best to treat it as a continuous variable. Treating a predictor as a continuous variable implies that a simple linear or polynomial function can adequately describe the relationship between the response and the predictor. When you treat a predictor as a categorical variable, a distinct response value is fit to each level of the variable without regard to the order of the predictor levels. Use this information, in addition to the purpose of your analysis to decide what is best for your situation.