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Measurement, Levels of
The rules determining the types of mathematical operations or statistical formulas that can be performed on a variable with a set of characteristics. Nominal variables are those in which differences are defined in terms of categories, such as gender, major, or political affiliation. Nominal variables are often coded numerically, although there is no inherent order in the scores. Central tendency for nominal variables can only be measured through the mode. Ordinal variables are categorical variables that can be ranked. Examples include year in college and order of finishers in a race. Central tendency for ordinal variables can be defined as the median or mode. Scores can be added and subtracted. Interval variables have the additional characteristic of having defined units of measurement but no true ...