perm.var.test: Permutation F test to compare two variances

In RVAideMemoire: Testing and Plotting Procedures for Biostatistics

Permutation F test to compare two variances

Description

Performs a permutation F test to compare two variances.

Usage

perm.var.test(x, ...)

## Default S3 method:
perm.var.test(x, y, ...)

## S3 method for class 'formula'
perm.var.test(formula, data, alternative = c("two.sided", "less",
  "greater"), nperm = 999, progress = TRUE, ...)

Arguments

x	a numeric vector of data values.
y	a numeric vector of data values.
formula	a formula of the form a ~ b where a gives the data values and b a factor with 2 levels giving the corresponding groups.
data	an optional data frame containing the variables in the formula formula. By default the variables are taken from environment(formula).
alternative	a character string specifying the alternative hypothesis, must be one of "two.sided" (default), "greater" or "less".
nperm	number of permutations.
progress	logical indicating if the progress bar should be displayed.
...	further arguments to be passed to or from other methods.

Details

The function deals with the limitted floating point precision, which can bias calculation of p-values based on a discrete test statistic distribution.

Value

method	name of the test.
statistic	test statistics of the parametric test.
permutations	number of permutations.
p.value	p-value of the permutation test.
estimate	the ratio of the two variances.
alternative	a character string describing the alternative hypothesis.
data.name	a character string giving the name(s) of the data.
null.value	the ratio of population variances under the null hypothesis, always 1.

Author(s)

Maxime HERVE <[e-mail]>

See Also

var.test

Examples

response <- c(rpois(8,1),rpois(8,3))
fact <- gl(2,8,labels=LETTERS[1:2])
perm.var.test(response~fact)

RVAideMemoire documentation built on Nov. 6, 2023, 5:07 p.m.