What is a nominal scale used for?

A nominal scale is used for classifying objects into categories without any quantitative value or order. This type of scale is designed to simply label or name different categories or groups based on qualitative characteristics. For instance, in surveys, you might see responses categorized as "yes," "no," or "maybe," or classes organized by types, such as "vegetables," "fruits," or "grains." The essential characteristic of nominal scales is that they provide a way to distinguish between different items or groups but do not imply any ranking or measurable difference among them.

Regarding the other options: measuring precise quantities pertains to interval or ratio scales, which allow for exact measurement. Ranking data points follows the principles of ordinal scales, where order matters but the exact differences between ranks are not defined. Comparing ratios relates to ratio scales, which provide meaningful comparison of values, supported by absolute zero and consistent intervals. Each of these scales serves distinct functions in data categorization and analysis, emphasizing why nominal scales are uniquely suited for classification without hierarchy or quantity.