Kappa: Cohen's Kappa and Weighted Kappa

In vcd: Visualizing Categorical Data

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"))
## S3 method for class 'Kappa'
print(x, digits=max(getOption("digits") - 3, 3),
CI=FALSE, level=0.95, ...)
## S3 method for class 'Kappa'
confint(object, parm, level = 0.95, ...)
## S3 method for class 'Kappa'
summary(object, ...)
## S3 method for class 'summary.Kappa'
print(x, ...)

Arguments

x	For Kappa: a confusion matrix. For the print methods: object of class "Kappa" or "summary.Kappa"
weights	either one of the character strings given in the default value, or a user-specified matrix with same dimensions as x.
digits	minimal number of significant digits.
CI	logical; shall confidence limits be added to the output?
level	confidence level between 0 and 1 used for the confidence interval.
object	object of class "Kappa".
parm	Currently, ignored.
...	Further arguments passed to the default print method.

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 columns/rows, and the Fleiss-Cohen weights by 1 - |i - j|^2 / (r - 1)^2. The latter one attaches greater importance to near disagreements.

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.

Note

The summary method also prints the weights.

There is a confint method for computing approximate confidence intervals.

Author(s)

David Meyer [e-mail]

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")
K <- Kappa(SexualFun)
K
confint(K)
summary(K)
print(K, CI = TRUE)

vcd documentation built on Sept. 17, 2024, 1:08 a.m.