2.2 Categorical and Numerical Data

Variables come in several types, depending on the data in the column. Most variables consist of either categorical or numerical data. Categorical variables are sometimes called qualitative or nominal variables, and numerical variables are sometimes called quantitative or continuous variables. The type of a variable, numerical or categorical, is important because the type determines how best to analyze the variable.

Categorical variables identify group membership. The labels within the column identify the observations that belong to each group. Most of the columns in Table 2.2 are categorical variables. For example, the first column names the customer making the purchase, and the fourth column names the item. ...

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