# permute.groups: Does randomisation test for the difference in means of two... In emon: Tools for Environmental and Ecological Survey Design

## Description

Does randomisation test for the difference in means mu1, mu2 of two vectors `v1` and `v2`. Can do one or two sided tests.

## Usage

 `1` ```permute.groups(v1, v2, alternative, nreps) ```

## Arguments

 `v1` Data vector for variable 1 `v2` Data vector for variable 2 `alternative` A character string specifying the alternative hypothesis, must be one of `"two.sided"` (default), `"greater"` (`mu1>mu2`) or `"less"`. You can specify just the initial letter. `nreps` Number of replications used in the randomisation and generation of the p-value. Default is `nreps=999`

## Details

Under the null hypothesis that `mu1=mu2`, the labelling of the `n1+n2` observations is unimportant. Therefore, we can generate the null distribution for the test statistic `m1-m2` or `|m1-m2|` depending on whether a one or two sided test is required) by randomly permuting the treatment labels nreps times and calculating the test statistic each time. The p-value is calculated as suggested by Manly (2006).

## Value

The p-value is returned as `\$p.value`

## Author(s)

Jon Barry: [email protected]

## References

Manly BFJ (2006) Randomization, Bootstrap And Monte Carlo Methods in Biology: 3rd edition. Chapman and Hall.

`power.groups`, `permute.BACI`

## Examples

 ```1 2 3 4``` ```set.seed(5) v1 = rnorm(27,10,2); v2=rnorm(25,11,2) permute.groups(v1, v2, alternative="two") permute.groups(v1, v2, alt="l") ```

emon documentation built on May 30, 2017, 1:42 a.m.