U Can: Statistics For Dummies

Chapter 20

Two-Way Tables and Independence

In This Chapter

Setting up two-way tables with categorical variables

Delving into marginal, joint, and conditional distributions

Checking for independence and dependence

Having perspective on the results of two-way tables

Categorical variables place individuals into groups based on certain characteristics, behaviors, or outcomes, such as whether you ate breakfast this morning (yes, no) or political affiliation (Democrat, Republican, Independent, “other”). Oftentimes people look for relationships between two categorical variables; hardly a day goes by that you don’t hear about another relationship that’s reported to have been found.

Here are just a few examples we found on the Internet recently:

• Dog owners are more likely to take their animal to the vet than cat owners.
• Heavy use of social-networking websites in teens is linked to depression.
• Children who play more video games do better in science classes.

With all this information being given to you about variables that are related, how do you decide what to believe? For example, does ...