vcd (version 1.1-1)

Kappa: Cohen's Kappa and Weighted Kappa

Description

Computes two agreement rates: Cohen's kappa and weighted kappa, and confidence bands.

Usage

Kappa(x, weights = c("Equal-Spacing", "Fleiss-Cohen"))

Arguments

x

a confusion matrix.

weights

either one of the character strings given in the default value, or a user-specified matrix with same dimensions as x.

Value

• An object of class "Kappa" with three components:
• Unweighted
  numeric vector of length 2 with the kappa statistic (value component), along with Approximate Standard Error (ASE component)
• Weighted
  idem for the weighted kappa.
• Weights
  numeric matrix with weights used.

Details

Cohen's kappa is the diagonal sum of the (possibly weighted) relative frequencies, corrected for expected values and standardized by its maximum value. The equal-spacing weights are defined by $1 - |i - j| / (r - 1)$, $r$ number of colums/rows, and the Fleiss-Cohen weights by $1 - |i - j|^2 / (r - 1)^2$. The latter one attaches greater importance to near disagreements.

References

Cohen, J. (1960), A coefficient of agreement for nominal scales. Educational and Psychological Measurement, 20, 37--46.

Everitt, B.S. (1968), Moments of statistics kappa and weighted kappa. The British Journal of Mathematical and Statistical Psychology, 21, 97--103.

Fleiss, J.L., Cohen, J., and Everitt, B.S. (1969), Large sample standard errors of kappa and weighted kappa. Psychological Bulletin, 72, 332--327.

See Also

agreementplot, confint

Examples

data("SexualFun")
Kappa(SexualFun)