pairwise.t.test
Pairwise t tests
Calculate pairwise comparisons between group levels with corrections for multiple testing
 Keywords
 htest
Usage
pairwise.t.test(x, g, p.adjust.method = p.adjust.methods, pool.sd = !paired, paired = FALSE, alternative = c("two.sided", "less", "greater"), ...)
Arguments
 x
 response vector.
 g
 grouping vector or factor.
 p.adjust.method
 Method for adjusting p values (see
p.adjust
).  pool.sd
 switch to allow/disallow the use of a pooled SD
 paired
 a logical indicating whether you want paired ttests.
 alternative
 a character string specifying the alternative
hypothesis, must be one of
"two.sided"
(default),"greater"
or"less"
. Can be abbreviated.  ...
 additional arguments to pass to
t.test
.
Details
The 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 t.test
,
so extra arguments are ignored. Pooling does not generalize to paired tests
so pool.sd
and paired
cannot both be TRUE
.
Only the lower triangle of the matrix of possible comparisons is being
calculated, so setting alternative
to anything other than
"two.sided"
requires that the levels of g
are ordered
sensibly.
Value

Object of class
"pairwise.htest"
See Also
Examples
library(stats)
attach(airquality)
Month < factor(Month, labels = month.abb[5:9])
pairwise.t.test(Ozone, Month)
pairwise.t.test(Ozone, Month, p.adj = "bonf")
pairwise.t.test(Ozone, Month, pool.sd = FALSE)
detach()
Community examples
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