Which of the following data types must be used when working with variables that require classification into two or more groups before analysis?

Discrete data refers to numerical data that can only take specific, fixed values (e.g., number of children), not classifications into groups.

Numerical data represents quantities that can be measured and ordered, either discrete or continuous, and is not primarily for classification.

Alphanumeric data is a general term for data containing letters, numbers, and symbols, and while it can represent categorical data, 'categorical' is the more specific and correct data type term for classification purposes.

Categorical data refers to data that can be divided into groups or categories, such as 'male/female,' 'country,' or 'product type.' This data type is specifically used for classification into two or more distinct groups, making it suitable for analysis that involves grouping or counting observations within these categories.