Which statement best describes the difference between nominal and ordinal data?

• A. Nominal data have categories with meaningful order; ordinal data do not.
• B. Nominal data are numerical; ordinal data are not.
• C. Nominal data have categories with no intrinsic order; ordinal data have a meaningful order.
• D. Nominal data can be ranked; ordinal data have no order.

Answer: (C)

Nominal vs ordinal data differ in whether the categories have an order. Nominal data label categories without any natural ranking—think of blood type or types of fruit. You can count how many fall into each category, but you can’t say one category is higher or lower than another. Ordinal data arrange categories in a meaningful sequence—like pain levels (none, mild, moderate, severe) or disease stages (I, II, III). You can say that one category is above another, but you don’t assume equal intervals between steps, so you can’t quantify the exact difference between levels.

This is why the statement describing nominal data as having categories with no intrinsic order and ordinal data as having a meaningful order is the best. The other descriptions mix up whether the data are purely labels, whether they are numerical, or whether ranking is possible, which doesn’t capture the essential distinction between nominal and ordinal.