How To Create A Contingency Table

When evaluating the relationship between two or more different items or variables from an experiment, use a contingency table. This table allows for an at-a-glance analysis of observations between the variables. The most common type of contingency table is commonly referred to as the 2x2 or 2 row and 2 column contingency table, but can have as many rows and columns as needed for variables to be evaluated.

Step 1

Start with two outcomes. In this example, we will use pass versus fail. These are the columns in the table.

Step 2

Define the group variables. In our example, these will be the classes. They will be the rows for the table.

\(Pass Fail\)

Class 1 A B Class 2 C D

Step 3

Input the numbers. Instead of A, B, C and D in our example, we'll use some fictional numbers of students who passed and failed tests. In a real contingency table, numbers will be used, not variables.

\(Pass Fail\)

Class 1 13 7 Class 2 19 1

Step 4

Tally both ends. This is called "two-tallied."

\(Pass Fail Total\)

Class 1 13 7 20 Class 2 19 1 20 Total 32 8 40

Compute the P-value. The formula is A/(A+B) – C/(C+D).