In statistics, a categorical variable is a variable that can take on one of a limited and usually fixed number of possible values, assigning each individual or other unit of observation to a particular group or nominal category on the basis of some qualitative property.

A stripplot is a single-axis scatter plot that is used to visualize the distribution of many individual one-dimensional values. The values are plotted as dots along one unique axis, and the dots with the same value can overlap.