## 20.11 Cochran-Mantel-Haenszel 卡方检验 mantelhaen.test

Performs a Cochran-Mantel-Haenszel chi-squared test of the null that two nominal variables are conditionally independent in each stratum, assuming that there is no three-way interaction.

usage(mantelhaen.test)
mantelhaen.test(x, y = NULL, z = NULL,
alternative = c("two.sided", "less", "greater"), correct = TRUE,
exact = FALSE, conf.level = 0.95)