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Kinds of data: Categorical

Categorical data is, as you might guess, data that fall into categories, or classes. There are 2 main types of categorical data. 

1.) Nominal data has no natural order or relationship. In the fruit shape example below, a score of 2 does not imply more than or better than a score of 1. The classes are just different.

To find a marker correlated with this type of data, you need only a test of independence (e.g. chi-square).