6.Scale
Though nominal is one of the specific categories of variable, scale is a more general distinction. In fact, any of the three formal types of variables can also be scale. To make the variable scale, a researcher would assign numbers to the nominal, ordinal or interval variables. For example, if the ordinal variable is socioeconomic status and there are five categories (poverty, lower class, middle class, upper-middle class and elite class), assigning the five options a number would make the variable scale. So, poverty would equal 1, lower class would equal 2 and so on.