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What is a contingency table?
Contingency tables are used to tabulate the actual number of subjects (or observations) that fall into the categories defined by the rows and columns of a table.
The rows and columns can be defined in different ways, based on experimental design.
| • | Prospective: You choose subjects based on exposure, from which you define the rows. Each column represents a different outcome. |
| • | Retrospective (case-control): Each column represents a different group of subjects, identified based on presence or absence of disease. Each row represents a different exposure they have had in the past. |
| • | Experiment: Each row represents a different treatment group. Each column represents a different outcome. |
| • | Cross-sectional: You select a group of subjects, and then categorize them by exposure (different rows) and disease (different columns). |
Analyses from a contingency table
| • | Odds ratios and relative risk |
Graph types from an contingency table:
Example of a contingency table:
| • | Each row represents a group. |
| • | Each column defines an outcome. |
| • | Enter the number of subjects that fall into the groups defined by a particular row and column. Enter the actual subject count -- not percents, not fractions, and not normalized rates. |
| • | Since a contingency table tabulates the number of subjects, it's not possible to enter negative values or fractions. |
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