median test
On Fri, May 28, 2010 at 6:58 AM, linda Porz <linda.porz at gmail.com> wrote:
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?
**Disclaimer: I have no idea what your data represents or how (in)appropriate any of these tests may be** R can do the tests you mentioned (and many more). Wilcoxon test: wilcox.test(x=group1, y=group2, paired=FALSE) see ?wilcox.test For testing the distribution look at: ?ks.test and ?pcauchy The code might be something along the lines of: ks.test(x=yourdata, y="pcauchy") Again I want to stress that you should know your data and what tests you are doing and why you are doing them. R will do just about whatever you want, including many things that you probably should not do. Josh
Many thanks, Linda 2010/5/27 Joshua Wiley <jwiley.psych at 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)$p.value that way it's less than or equal to the median. Hope that helps, Josh On Thu, May 27, 2010 at 7:24 AM, linda Porz <linda.porz at gmail.com> wrote:
Hi all,
I have found the following function online
median.test<-function(y1,y2){
?z<-c(y1,y2)
?g <- rep(1:2, c(length(y1),length(y2)))
?m<-median(z)
?fisher.test(z<m,g)$p.value
}
in
http://www.mail-archive.com/r-help at 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]]
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-- Joshua Wiley Senior in Psychology University of California, Riverside http://www.joshuawiley.com/
Joshua Wiley Senior in Psychology University of California, Riverside http://www.joshuawiley.com/