- Build contingency (two-way) tables.
Contingency Tables
We use a contingency table, sometimes called a two-way table, to organize data on two categorical variables at the same time.
two-way table
A two-way table, also known as a contingency table, is a table used in statistics to represent the relationship between two categorical variables.
A contingency table provides a way of portraying data for two categorical variables that can help calculate probabilities. The table displays sample values in relation to two different variables that may be dependent or contingent on one another.
Example
This table shows the number of athletes who stretch before exercising and how many had injuries within the past year.
| Injury in last year | No injury in last year | Total | |
|---|---|---|---|
| Stretch | [latex]55[/latex] | [latex]295[/latex] | [latex]350[/latex] |
| Does not stretch | [latex]231[/latex] | [latex]219[/latex] | [latex]450[/latex] |
| Total | [latex]286[/latex] | [latex]514[/latex] | [latex]800[/latex] |
- What proportion of athletes stretch before exercising?
- What proportion of athletes had no injury in the last year?
- Describe the cell with [latex]55[/latex] counts using a complete sentence.