RVAideMemoire (version 0.9-35)

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

Description

Perform a permutational F test to compare two variances.

Usage

perm.var.test(formula, data, ratio = 1, alternative = c("two.sided", "less",
  "greater"), nperm = 999)

Arguments

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).

ratio

the hypothesized ratio of the two population variances.

alternative

a character string specifying the alternative hypothesis, must be one of "two.sided" (default), "greater" or "less".

nperm

number of permutations.

Value

• method
  name of the test.
• statistic
  test statistics of the parametric test.
• permutations
  number of permutations.
• p.value
  p-value of the permutational 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.

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)