confintr (version 0.1.0)

cramersv: Cramer's V

Description

This function calculates Cramer's V, a measure of association between two categorical variables. It is a scaled version of the chi-squared test statistic and lies between 0 and 1. Cramer's V is calculated as sqrt(chi-squared / (n * (k - 1))), where n is the number of observations and k is the smaller of the number of levels of the two variables.

Usage

cramersv(x)

Arguments

x

The result of stats::chisq.test, a matrix/table of counts or a data.frame with exactly two columns representing the two variables.

Value

A numeric vector of length one.

Details

Yates continuity correction is never applied. So in the 2x2 case, if x is the result of stats::chisq.test, make sure no continuity correction was applied. Otherwise, results can be inconsistent.

References

Cramer, Harald. 1946. Mathematical Methods of Statistics. Princeton: Princeton University Press, page 282 (Chapter 21. The two-dimensional case).

Examples

# NOT RUN {
tab <- table(mtcars[c("am", "vs")])
chi <- chisq.test(tab, correct = FALSE)
cramersv(mtcars[c("am", "vs")])
cramersv(chi)
cramersv(tab)
# }