imam.Var.test {PairedData} | R Documentation |
Imam test of scale for paired samples
Description
Robust test of scale for paired samples based on absolute deviations from the trimmed means (or medians), called Imam test in Wilcox (1989).
Usage
imam.Var.test(x, ...)
## Default S3 method:
imam.Var.test(x, y = NULL,
alternative = c("two.sided", "less", "greater"),
mu = 0,conf.level = 0.95,location=c("trim","median"),
tr=0.1, ...)
## S3 method for class 'paired'
imam.Var.test(x, ...)
Arguments
x |
first sample or object of class paired. |
y |
second sample. |
alternative |
alternative hypothesis. |
mu |
the location parameter mu. |
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 paired t test is then carried out on the (global) ranks of X and Y.
Value
A list with class "htest" containing the components of a paired t test.
Author(s)
Stephane CHAMPELY
References
Wilcox, R.R. (1989) Comparing the variances of dependent groups. Psychometrika, 54, 305-315.
Conover, W.J. and Iman, R.L. (1981) Rank transformations as a bridge between parametric and nonparametric statistics. The American Statistician, 35, 124-129.
See Also
Var.test, grambsch.Var.test
Examples
z<-rnorm(20)
x<-rnorm(20)+z
y<-(rnorm(20)+z)*2
imam.Var.test(x,y)
# some variations
imam.Var.test(x,y,tr=0.2)
imam.Var.test(x,y,location="median")
data(anscombe2)
p<-with(anscombe2,paired(X1,Y1))
imam.Var.test(p)