scale, nominal

n. Nominal scales lack all three key scale properties: magnitude, equal intervals, and absolute zero. As such, nominal scales are simply a means of labeling or categorizing data but do not express any quantitative relationship among variables, categories, or values. For example, demographic data, such as sex, is often converted into a nominal scale for data entry by assigning the category 1 to men and 2 to women. These numbers serve solely as numerical labels and do not represent a quantitative relationship between variables. The only appropriate mathematical calculations for nominal data are frequency and mode. – BJM