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 t-tests.
- 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)
# NOT RUN {
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()
# }