Associations

While correlations concern only continuous data such as height, weight, age, and so on, associations concern categorical data such as gender [male; female], status of some sort [small; medium; large] and even continuous data that has been arranged in categories, such as height [short; average; tall] and age [30s; 40s; 50s; and so on].

There are two types of association that you need to be aware of:

• Categorical versus categorical
• Categorical versus continuous

To confuse things just a little bit more, there are two flavors of categorical data:

• Ordinal
• Nominal

Recall from Chapter 2, Your Statistical Toolbox, that ordinal data is categorical data that has a natural order to the categories, whereas nominal data categories have no natural order.

In this case, it can be useful to separate the categories into separate variables, each having two categories, as in Figure 4.3.

Figure 4.3: Separate the categories of nominal variables into separate columns...