| % File src/library/stats/man/pairwise.t.test.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2007 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{pairwise.t.test} |
| \alias{pairwise.t.test} |
| \title{ Pairwise t tests} |
| \description{ |
| Calculate pairwise comparisons between group levels with corrections |
| for multiple testing |
| } |
| \usage{ |
| pairwise.t.test(x, g, p.adjust.method = p.adjust.methods, |
| pool.sd = !paired, paired = FALSE, |
| alternative = c("two.sided", "less", "greater"), |
| \dots) |
| } |
| \arguments{ |
| \item{x}{ response vector. } |
| \item{g}{ grouping vector or factor. } |
| \item{p.adjust.method}{ Method for adjusting p values (see \code{\link{p.adjust}}). } |
| \item{pool.sd}{ switch to allow/disallow the use of a pooled SD } |
| \item{paired}{ a logical indicating whether you want paired |
| t-tests. } |
| \item{alternative}{ a character string specifying the alternative |
| hypothesis, must be one of \code{"two.sided"} (default), |
| \code{"greater"} or \code{"less"}. Can be abbreviated.} |
| \item{\dots}{ additional arguments to pass to \code{t.test}. } |
| } |
| \details{ The \code{pool.sd} switch calculates a common SD for all |
| groups and uses that for all comparisons (this can be useful if some |
| groups are small). This method does not actually call \code{t.test}, |
| so extra arguments are ignored. Pooling does not generalize to paired tests |
| so \code{pool.sd} and \code{paired} cannot both be \code{TRUE}. |
| |
| Only the lower triangle of the matrix of possible comparisons is being |
| calculated, so setting \code{alternative} to anything other than |
| \code{"two.sided"} requires that the levels of \code{g} are ordered |
| sensibly. |
| } |
| \value{ |
| Object of class \code{"pairwise.htest"} |
| } |
| \seealso{ \code{\link{t.test}}, \code{\link{p.adjust}}} |
| |
| \examples{ |
| attach(airquality) |
| Month <- factor(Month, labels = month.abb[5:9]) |
| pairwise.t.test(Ozone, Month) |
| pairwise.t.test(Ozone, Month, p.adjust.method = "bonf") |
| pairwise.t.test(Ozone, Month, pool.sd = FALSE) |
| detach() |
| } |
| \keyword{htest} |