N.cohen.kappa {irr}

Sample Size Calculation for Cohen's Kappa Statistic

Description

This function is a sample size estimator for the Cohen's Kappa statistic for a binary outcome. Note that any value of "kappa under null" in the interval [0,1] is acceptable (i.e. k0=0 is a valid null hypothesis).

Usage

 N.cohen.kappa(rate1, rate2, k1, k0, alpha=0.05, 
               power=0.8, twosided=FALSE)

Arguments

rate1

the probability that the first rater will record a positive diagnosis

rate2

the probability that the second rater will record a positive diagnosis

k1

the true Cohen's Kappa statistic

k0

the value of kappa under the null hypothesis

alpha

type I error of test

power

the desired power to detect the difference between true kappa and hypothetical kappa

twosided

TRUE if test is two-sided

Value

returns required sample size

Author(s)

Ian Fellows

References

Cantor, A. B. (1996) Sample-size calculation for Cohen's kappa. Psychological Methods, 1, 150-153.

See Also

kappa2

Examples

  # Testing H0: kappa = 0.7 vs. HA: kappa > 0.7 given that
  # kappa = 0.85 and both raters classify 50% of subjects as positive.
  N.cohen.kappa(0.5, 0.5, 0.7, 0.85)