Contingency Table

Synonyms

2 × 2 table

Definition

A contingency table generally is a representation of categorical data in a tabular format, such as a 2 × 2 table, though the table can have three or more variables. There are row variables on the horizontal axis and column variables on the vertical axis. It represents mutually exclusive variables. Good examples of contingency tables are hit rate, sensitivity, and specificity, as well as positive and negative predictive power. In the case of hit rates to assess the number of correct classification decisions that result from the use of a particular test or measure, one would enter the number of true positives, true negatives, false positives, and true negatives into a contingency table like the one below.

	Cond. +	Cond. −
Test +	True + (TP)	False + (FP)	Total + decisions
Test −	False − (FN)	True − (TN)	Total − decisions
	Base rate	Cond. Absent	Total of all decisions

1. Cond. Condition

In this example hit rate would be calculated by adding the number of true...