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st: R: Kruskal-Wallis equality-of-populations rank test


From   "Carlo Lazzaro" <carlo.lazzaro@tin.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: R: Kruskal-Wallis equality-of-populations rank test
Date   Sat, 13 Nov 2010 12:17:05 +0100

Momo wrote:

"-2- some variables I got results with 1st type 1st var as follows.

chi-squared = 290.697 with 172 d.f.
probability = 0.0001

chi-squared with ties = 388.261 with 172 d.f.
probability = 0.0001"

Whenever groups of tied scores come alive in KruskalWallis (KW) test, the
ranks that should be assigned are averaged, and the average rank is
assigned, instead.
The test statistic T is different in presence and in absence of ties: this
explains the difference in the results Stata gave you excluding and
including ties.

For more on KW (pag. 288-300) and on nonparametric tests at large, I would
recommend you to look up to Conover WJ. Practical nonparametric statistics.
Third ed. New York: Wiley, 1999.

Kind Regards,
Carlo

----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di momo
Inviato: venerdì 12 novembre 2010 15.38
A: statalist@hsphsun2.harvard.edu
Oggetto: st: Kruskal-Wallis equality-of-populations rank test

Dear Colleagues

I am using KW test to check the differences between Four different types of
companies and I use four variables, so I check for each variables on each
type each time. I mean the 1st var on 1st type, the 2nd var on 1st type and
so on..

1- so with some variables stata don't do the test and gives me "too many
values" where I am using stata 11.

2- some variables I got results with 1st type 1st var as follows.

chi-squared = 290.697 with 172 d.f.
probability = 0.0001

chi-squared with ties = 388.261 with 172 d.f.
probability = 0.0001

whats the differences between the values.
so any help in explanation highly appreciated.

Thanks in advance
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