Pairwise Test for Multiple Comparisons of normal scores (van der Waerden test)
Description
Calculate pairwise multiple comparisons between group levels according to van der Waerden.
Usage
1 2 3 4 5 6 7 8 9  posthoc.vanWaerden.test(x, ...)
## Default S3 method:
posthoc.vanWaerden.test( x, g, p.adjust.method =
p.adjust.methods, ...)
## S3 method for class 'formula'
posthoc.vanWaerden.test(formula, data, subset,
na.action, p.adjust.method = p.adjust.methods, ...)

Arguments
x 
a numeric vector of data values, or a list of numeric data vectors. 
g 
a vector or factor object giving the group for the
corresponding elements of 
formula 
a formula of the form 
data 
an optional matrix or data frame (or similar: see

subset 
an optional vector specifying a subset of observations to be used. 
na.action 
a function which indicates what should happen when
the data contain 
p.adjust.method 
Method for adjusting p values (see 
... 
further arguments to be passed to or from methods. 
Details
For onefactorial designs with samples that do not meet the assumptions
for onewayANOVA and subsequent posthoc tests, the van der Waerden
test vanWaerden.test
using normal scores can be
employed. Provided that significant differences were detected by this
global test, one may be interested in applying posthoc tests according
to van der Waerden for pairwise multiple comparisons of the group levels.
First, the data are ranked according to KruskalWallis. Second, the ranks are transformed to normal scores. The group means of normal scores and the total variance is used to calculate quantiles of the studenttdistribution and consequent pvalues.
See vignette("PMCMR")
for details.
Value
A list with class "PMCMR"
method 
The applied method. 
data.name 
The name of the data. 
p.value 
The twosided pvalue of the studenttdistribution. 
statistic 
The estimated quantile of the studenttdistribution. 
p.adjust.method 
The applied method for pvalue adjustment. 
Note
There is no tie correction applied in this function.
Author(s)
Thorsten Pohlert
References
W. J. Conover and R. L. Iman (1979), On multiplecomparisons procedures, Tech. Rep. LA7677MS, Los Alamos Scientific Laboratory.
See Also
kruskal.test
,
vanWaerden.test
,
posthoc.kruskal.nemenyi.test
,
posthoc.kruskal.dunn.test
,
TDist
,
p.adjust
Examples
1 2 3 4 5 6 7 8  ##
require(stats)
data(InsectSprays)
attach(InsectSprays)
vanWaerden.test(count, spray)
posthoc.vanWaerden.test(count, spray, "bonferroni")
detach(InsectSprays)
rm(InsectSprays)
