The ubiquitous 2X2 table, its parameters and their confidence limits.

The confidence limits for all parameters derived from a 2X2 contingency table are uniquely determined by the limiting matrices that arise from adding or subtracting certain values to or from the four cell entries. Various methods to determine these addends are discussed and a computer program is presented that produces reliable results. The limiting matrices thus produced bypass the more complicated expressions for the standard errors of the many epidemiological parameters that are used to interpret the 2X2 table.