[R] Glitch in Kruskal-Wallis test?

[Jenny Liu]

Thank you very much Michael and Bert! I'll have to look for some other
statistical test. Have a great holiday!

On Sat, Dec 22, 2018, 10:36 AM Bert Gunter <bgunter.4567 using gmail.com wrote:

> ... Moreover, you should not analyze proportions in this way, which treats
> .5 = 2/4 or .5 = 2000/4000 identically. As David said, you need to work
> with a statistician.
>
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along and
> sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Sat, Dec 22, 2018 at 7:32 AM David L Carlson <dcarlson using tamu.edu> wrote:
>
>> You may need to spend some more time with the statistician who needs to
>> see your data. It is not clear if you have a two sample test or a paired
>> sample test. Kruskall-Wallis expects data for each observation, not grouped
>> data. Without the observations, the test cannot compute the sample size and
>> the degrees of freedom. You have run kruskal.test separately on each
>> sample. The kruskal.test is designed for comparing two or more samples.
>>
>> ----------------------------------------
>> David L Carlson
>> Department of Anthropology
>> Texas A&M University
>> College Station, TX 77843-4352
>>
>> -----Original Message-----
>> From: R-help <r-help-bounces using r-project.org> On Behalf Of Jenny Liu
>> Sent: Saturday, December 22, 2018 7:10 AM
>> To: Michael Dewey <lists using dewey.myzen.co.uk>
>> Cc: r-help using r-project.org
>> Subject: Re: [R] Glitch in Kruskal-Wallis test?
>>
>> Hi Michael,
>>
>> Thank you for your reply! I'm testing the difference in proportions. Temp
>> is temperature, and Prop is the proportion of insect pupae that survived
>> at
>> that temperature. I was told by a statistician that the K-W was
>> appropriate
>> for testing proportions, but perhaps you know of an alternative? I have
>> already tested for heteroscedasticity using the Breusch-Pagan test.
>>
>> Thanks again,
>> Jenny
>>
>>
>>
>> On Dec 22, 2018 7:38 AM, "Michael Dewey" <lists using dewey.myzen.co.uk> wrote:
>>
>> Dear Jenny
>>
>> What exactly do you think you are testing here? You are telling K-W you
>> have seven groups each with a single value which is not the usual
>> situation for K-W.
>>
>> Michael
>>
>>
>> On 22/12/2018 04:58, Jenny Liu wrote:
>> > Hi everyone,
>> > I have been running a K-W test with the attached data, PupMort1. My
>> code:
>> > kruskal.test(Prop~Temp,data=PupMort1)
>> > However, I found that I get the exact same result when I change the
>> x-values, as
>> > in the attached data PupMort2.
>> > Test run with PupMort1Kruskal-Wallis rank sum testdata:  Prop by Temp
>>
>> > Kruskal-Wallis chi-squared = 6, df = 6, p-value = 0.4232
>> > Test run with PupMort2Kruskal-Wallis rank sum testdata:  Prop by Temp
>>
>> > Kruskal-Wallis chi-squared = 6, df = 6, p-value = 0.4232
>> > Does anybody know why this is happening?
>> > Thank you!
>> > Jenny
>> >
>> >
>> > ______________________________________________
>> > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
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>> > PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>> >
>>
>> --
>> Michael
>> http://www.dewey.myzen.co.uk/home.html
>>
>>         [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.
>>
>

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