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 `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`

.

Object of class `"pairwise.htest"`

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.

# 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() # }