What is nominal data?

Nominal data are categorical data where the order of the categories is arbitrary. A good example is race/ethnicity has values 1=White, 2=Hispanic, 3=American Indian, 4=Black, 5=Other. Note that the order of the categories is arbitrary.

Certain statistical concepts are meaningless for nominal data. For example it would be silly to ask what are the mean and standard deviation are for race/ethnicity.

This webpage was written by Steve Simon on 2002-10-11, edited by Steve Simon, and was last modified on 2008-07-08. This page needs major revisions. Category: Definitions.