pairwise.t.test {stats} | R Documentation |
Calculate pairwise comparisons between group levels with corrections for multiple testing
pairwise.t.test(x, g, p.adjust.method = p.adjust.methods, pool.sd = !paired, paired = FALSE, alternative = c("two.sided", "less", "greater"), ...)
x |
response vector. |
g |
grouping vector or factor. |
p.adjust.method |
Method for adjusting p values (see |
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 |
... |
additional arguments to pass to |
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.
Object of class "pairwise.htest"
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()