[R] chi-Squared distribution in Friedman test

[Uwe Ligges]

Prasanna Balaprakash wrote:

> Dear R helpers:
> 
> 
> Thanks for the previous reply. I am using Friedman racing test. According the the book "Pratical Nonprametric Statistic" by WJ Conover, after computing the statistics, he suggested to use chi-squared or F distribution to accept or reject null hypothesis. After looking into the source code, I found that R uses chi-sqaured distribution as below:
> 
> PVAL <- pchisq(STATISTIC, PARAMETER, lower = FALSE)
> 
> but still I cant figure out why they are using this pschisq insted of dchisq. Sorry I am wrong!!

You want to get the distribution function rather than the density.

Uwe Ligges


> 
> Thanking you
> truly
> Prasanna
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>>----- Original Message ----- 
>>From: "Dimitris Rizopoulos" <dimitris.rizopoulos at med.kuleuven.ac.be>
>>To: "Prasanna Balaprakash" <pbalapra at ulb.ac.be>
>>Cc: <r-help at stat.math.ethz.ch>
>>Sent: Friday, January 21, 2005 1:05 PM
>>Subject: Re: [R] chi-Squared distribution
>>
>>
>>
>>>if you check ?qchisq, you'll see that the second
>>
>>My mistake, the third argument
>>
>>
>>>argument of the function denotes the non-centrality parameter! Try
>>>
>>>qchisq(0.75, 1:3)
>>>
>>>to get your answer.
>>>
>>>Best,
>>>Dimitris
>>>
>>>----
>>>Dimitris Rizopoulos
>>>Ph.D. Student
>>>Biostatistical Centre
>>>School of Public Health
>>>Catholic University of Leuven
>>>
>>>Address: Kapucijnenvoer 35, Leuven, Belgium
>>>Tel: +32/16/336899
>>>Fax: +32/16/337015
>>>Web: http://www.med.kuleuven.ac.be/biostat
>>>    http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm
>>>
>>>
>>>----- Original Message ----- 
>>>From: "Prasanna Balaprakash" <pbalapra at ulb.ac.be>
>>>To: <r-help at stat.math.ethz.ch>
>>>Sent: Friday, January 21, 2005 12:27 PM
>>>Subject: [R] chi-Squared distribution
>>>
>>>
>>>
>>>>Dear Rs:
>>>>
>>>>
>>>>outer(1:3, 1:3, function(df1, df2) qf(0.95, df1, df2))
>>>>
>>>>I compare this F distribution results with the table, the answers 
>>>>were perfect. But I need to see for chi-sqaured distribution. When 
>>>>I employed the similar formula
>>>>
>>>>outer(1:3, 1:3, function(df1, df2) qchisq(0.95, df1, df2)) , I am 
>>>>getting unexpected results. I need to see the following values:
>>>>
>>>>    p=0.750  .....
>>>>1     1.323
>>>>
>>>>2     2.773
>>>>
>>>>3     4.108
>>>>
>>>>
>>>>Thanking you
>>>>Prasanna
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>Prasanna Balaprakash,
>>>>Université Libre de Bruxelles,
>>>>50, Av. F. Roosevelt, CP 194/6,
>>>>B-1050 Brussels,
>>>>Belgium.
>>>>
>>>>______________________________________________
>>>>R-help at stat.math.ethz.ch mailing list
>>>>https://stat.ethz.ch/mailman/listinfo/r-help
>>>>PLEASE do read the posting guide! 
>>>>http://www.R-project.org/posting-guide.html
> 
> 
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