R: Sandvik-Olsson test of scale for paired samples

sandvikolsson.Var.test

R Documentation

Sandvik-Olsson test of scale for paired samples

Description

Robust test of scale for paired samples based on the absolute deviations from the trimmed means (or medians).

Usage

sandvikolsson.Var.test(x, ...)

## Default S3 method:
sandvikolsson.Var.test(x, y = NULL,
            alternative = c("two.sided", "less", "greater"),
            mu = 0, exact = NULL, correct = TRUE,
            conf.int = FALSE, conf.level = 0.95,location=c("trim","median"),tr=0.1, ...)

## S3 method for class 'paired'
sandvikolsson.Var.test(x, ...)

Arguments

`x`	first sample or object of class paired.
`y`	second sample.
`alternative`	alternative hypothesis.
`mu`	the location parameter mu.
`exact`	a logical indicating whether an exact p-value should be computed.
`correct`	a logical indicating whether to apply continuity correction in the normal approximation for the p-value.
`conf.int`	a logical indicating whether a confidence interval should be computed.
`conf.level`	confidence level.
`location`	location parameter for centering: trimmed mean or median.
`tr`	percentage of trimming.
`...`	further arguments to be passed to or from methods.

Details

The data are transformed as deviations from the trimmed mean: X=abs(x-mean(x,tr=0.1)) and Y=(y-mean(y,tr=0.1)). A wilcoxon signed-rank test is then carried out on X and Y.

Value

A list with class "htest" containing the components of a wilcoxon signed-rank test.

Author(s)

Stephane CHAMPELY

References

Sandvik, L. and Olsson, B. (1982) A nearly distribution-free test for comparing dispersion in paired samples. Biometrika, 69, 484-485.

Examples

z<-rnorm(20)
x<-rnorm(20)+z
y<-(rnorm(20)+z)*2
sandvikolsson.Var.test(x,y)

p<-paired(x,y)
sandvikolsson.Var.test(p)


# some variations
sandvikolsson.Var.test(p,tr=0.2)
sandvikolsson.Var.test(p,location="median")