Ratio measure refers to the highest (most complex) level of measurement that a variable can possess. The properties of a variable that is a ratio measure are the following: (a) Each value can be treated as a unique category (as in a nominal measure); (b) different values have order of magnitude, such as greater than or less than or equal to (as in an ordinal measure); (c) basic mathematical procedures can be conducted with the values, such as addition and division (as with an interval measure); and (d) the variable can take on the value of zero. An example of a ratio measure is someone's annual income.

A ratio measure may be expressed as either a fraction or percentage; in addition, a ratio measure may be ...