Biostatistics For Dummies

Chapter 14

Taking a Closer Look at Fourfold Tables

In This Chapter

Beginning with the basics of fourfold tables

Digging into sampling designs for fourfold tables

Using fourfold tables in different scenarios

In Chapter 13, I show you how to compare proportions between two or more groups with a cross-tab table. In general, a cross-tab shows the relationship between two categorical variables. Each row of the table represents one particular category of one variable, and each column of the table represents one particular category of the other variable. The table can have two or more rows and two or more columns, depending on the number of levels (different categories) present in each of the two variables. So a cross-tab between a treatment variable that has three levels (like old drug, new drug, and placebo) and an outcome variable that has five levels (like died, got worse, unchanged, improved, and cured) has three rows and five columns.

A special case occurs when both variables are dichotomous (or binary); that is, they both have only two values, like gender (male and female) and compliance (good and bad). The cross-tab of these two variables has two rows and two columns. Because ...