In categorical data each observation falls into one of a number of distinct categories. Thus a categorical variable has a number of distinct categories. Such data are common in everyday life. Some examples of pairs of categorical variables are:
- gender and pet preference between cat and dog
- favourite television show and favourite holiday activity
- gender and favourite food
- favourite sport and colour of hair (e.g. redhead, blond, brown, black).
Sometimes the categories are natural, such as with gender or preference between cat and dog, and sometimes they require choice and careful description, such as favourite holiday activity or favourite food.