[R] Cohen's Kappa

[Christian Schulz]

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