Hello,

I can't have different data these data came from mice that have lived under
certain condition in the lab! I have just read the mentioned publication
"Should the median test be retired from general use?" It says in the
conclusion "If one felt that the data could not come from a Cauchy or slash
distribution, the Wilcoxon should be used."! What is this? Is there is any
test in R for a Cauchy or slash distribution? Can I used the unpaired
Wilcoxon, or I have a Cauchy distributed data?

Many thanks,
Linda

2010/5/27 Joshua Wiley <jwiley.psych@gmail.com>

> Hello Linda,
>
> The "problem" is actually the median of your data.  What the function
> median.test() does first is combine both groups.  Look at this:
>
> median(c(group1, group2))
>
> the median is 1, but the lowest value of the groups is also 1.  So
> when the function does the logical check z < m where z = c(group1,
> group2) and m is the median, there are no values that are less than
> the median value.  Therefore there is only 1 level, and the fisher
> test fails.
>
> You would either need different data or adjust the function to be:
>
> fisher.test(z <= m, g)$p.value
>
> that way it's less than or equal to the median.
>
> Hope that helps,
>
> Josh
>
> On Thu, May 27, 2010 at 7:24 AM, linda Porz <linda.porz@gmail.com> wrote:
> > Hi all,
> >
> > I have found the following function online
> >
> > median.test<-function(y1,y2){
> >  z<-c(y1,y2)
> >  g <- rep(1:2, c(length(y1),length(y2)))
> >  m<-median(z)
> >  fisher.test(z<m,g)$p.value
> > }
> >
> > in
> >
> > http://www.mail-archive.com/r-help@r-project.org/msg95278.html
> >
> > I have the following data
> >
> >> group1 <- c(2, 2, 2, 1, 4, 3, 1, 1)
> >> group2 <- c(3, 1, 3, 1, 4, 1, 1, 1, 7, 1, 1, 1, 1, 1, 2)
> >> median.test(w1,group1)
> > [1] 1
> >> median.test(group1,group2)
> > Error in fisher.test(z < m, g) : 'x' and 'y' must have at least 2 levels
> >
> > I am very thankful in advance for any suggestion and help.
> >
> > Regards,
> > Linda
> >
> >        [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>
>
> --
> Joshua Wiley
> Senior in Psychology
> University of California, Riverside
> http://www.joshuawiley.com/
>

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