A categorical variable indicating rank order, such as small, medium, and large, is the definition of _________ variable.

A categorical variable indicating rank order, such as small, medium, and large, defines an ordinal variable. Ordinal variables have categories that can be ranked or ordered meaningfully in relation to one another, unlike nominal variables which simply classify data without any provided order. The terms small, medium, and large are expressed in a sequence where one can tell that medium is larger than small but smaller than large, illustrating the inherent ranking among these categories.

In contrast, nominal variables do not possess an inherent order—categories such as gender or color cannot be logically arranged in a sequential manner. Dependent and independent variables relate to different levels of measurement and are primarily used in the context of statistics and hypothesis testing, where they denote relationships between variables rather than orders within categories. Therefore, the appropriate classification of the given variable as ordinal is supported by the way it implies a ranking system among its categories.