[R] chisq.test

[Rolf Turner]

On 27/06/12 08:54, arun wrote:
>
> Hi,
>
> The error is due to less than 5 observations in some cells.

     NO, NO, NO!!!!  It's not the observations that matter, it is
     the ***EXPECTED COUNTS***.  These must all be at least
     5 in order for the null distribution of the test statistic to be
     adequately approximated by a chi-squared distribution.

         cheers,

             Rolf Turner
>
> You can try,
> fisher.test(tabele)
>      Fisher's Exact Test for Count Data
>
> data:  tabele
> p-value = 0.0998
> alternative hypothesis: two.sided
>
> A.K.
>
>
>
> ----- Original Message -----
> From: Omphalodes Verna <omphalodes.verna at yahoo.com>
> To: "r-help at r-project.org" <r-help at r-project.org>
> Cc:
> Sent: Tuesday, June 26, 2012 2:27 PM
> Subject: [R] chisq.test
>
> Dear list!
>
> I would like to calculate "chisq.test" on simple data set with 70 observations, but the output is ''Warning message:''
>
> Warning message:
> In chisq.test(tabele) : Chi-squared approximation may be incorrect
>
>
> Here is an example:
>
>          tabele <- matrix(c(11, 3, 3, 18, 3, 6, 5, 21), ncol = 4, byrow = TRUE)
>          dimnames(tabela) <- list(
>          "SEX" = c("M","F"),
>          "HAIR" = c("Brown", "Black", "Red", "Blonde"))
>          addmargins(tabele)
>          prop.table(tabele)
>          chisq.test(tabele)
> Please, give me an advice / suggestion / recommendation.
>
> Thanks a lot to all, OV
>
>      [[alternative HTML version deleted]]
>
>
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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.
>