R: Cohen's Kappa and Weighted Kappa

Kappa {vcd} | R Documentation

## 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 - abs(i - j) / (r - 1), r number of columns/rows, and the Fleiss-Cohen weights by 1 - abs(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 David.Meyer@R-project.org

### 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)

[Package vcd version 1.4-4 Index]