Drexel dragonThe Math ForumDonate to the Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.

Math Forum » Discussions » sci.math.* » sci.stat.math.independent

Topic: kolmogov-smirnov, wilcoxon and kruskal tests
Replies: 14   Last Post: Dec 31, 2012 6:38 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]

Posts: 5
Registered: 12/22/12
kolmogov-smirnov, wilcoxon and kruskal tests
Posted: Dec 22, 2012 8:22 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Hi Everybody,

I'm trying to do some hypotheses testing in R and I have problems with interpretation of results.

I have two data sets:
> x<-c(2,1,1,2,2,3,2,2,1,2,2,4,1,2,4,1,1,5,2,1,4,2,2,1,1,2,2,1)
> y<-c(2,2,1,1,2,2,1,4,1,4,2,4,4,4,3,2,4,4,3,2,4,5)

according to the KS test they come from the same distribution:
> ks.test(x,y)

If they come from the same distribution all the characteristics (mean, median, ... ) should be the same.
However, Wicoxon and Kruskal tests indicate that their null hypothesis should be rejected:
> wilcox.test(x,y)
> kruskal.test(list(x,y))

Now, I am puzzled with the outcome of the test.
I can simply imagine a situation when Wilcox and Kruskal tests indicate that their null hypothesis should be accepted but the KS test can indicate that samples comes from different distributions. Here, it is the other way round. Does any one has some hints what causes the problems?


Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2015. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.