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st: R: Kruskal-Wallis equality-of-populations rank test
From
"Carlo Lazzaro" <[email protected]>
To
<[email protected]>
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 Kruskal Wallis (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: [email protected]
[mailto:[email protected]] Per conto di momo
Inviato: venerdì 12 novembre 2010 15.38
A: [email protected]
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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