[R] Cohen's Kappa

[Andrew Perrin]

Shouldn't that be

kappa = rater1 - rater2 / (1-chance)

?

Andy

----------------------------------------------------------------------
Andrew J Perrin - andrew_perrin (at) unc.edu - http://perrin.socsci.unc.edu
Assistant Professor of Sociology; Book Review Editor, _Social Forces_
University of North Carolina - CB#3210, Chapel Hill, NC 27599-3210 USA
New Book: http://www.press.uchicago.edu/cgi-bin/hfs.cgi/00/178592.ctl



On Thu, 22 Mar 2007, Christian Schulz wrote:

> Hi,
>
> im little bit confused about Cohen's Kappa and i should  be look into the
> Kappa function code. Is the easy formula really wrong?
>
> kappa=agreement-chance/(1-chance)
>
> many thanks
> christian
>
> ###############################################################################
> true-negativ:7445
> false-positive:3410
> false-negativ:347
> true-positiv:772
>
> classification-aggrement:68,6%
> kappa=agreement-chance/(1-chance) = (0.686-0.5)/0.5=0.372
>
> .....with function from library(vcd)
> Kappa(matrix(c(7445,3410,347,772),nrow=2))
>               value         ASE
> Unweighted 0.1686882 0.011235188
> Weighted   0.1686882 0.007979293
>
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