Dear R-help Team, I am from India and have a query on 'N.cohen.kappa' Sample size calculations for Cohen's Kappa Statistic. I have calculated manually the sample size using the formula mentioned in "Cantor, A. B. (1996) Sample-size calculation for Cohen’s kappa. Psychological Methods, 1, 150- 153". Later came to know that it can be done using the R 'irr' package. I got a different number.
Let us consider the following two situations: For situation 1, the sample size is 1370 using R Testing H0: kappa = 0.81 vs. HA: kappa> 0.95 given that kappa = 0.95 and both raters classify 1.5% of subjects as positive. R command used is: N.cohen.kappa(0.015, 0.015, 0.95, 0.81, alpha=0.05, power=0.8, twosided=FALSE ). But for the same situation, the sample size is much higher by manual calculation, which is 8580. For situation 2, the sample size is 74 by using R and is matching with the manual calculation too. Testing H0: kappa = 0.81 vs. HA: kappa> 0.95 given that kappa = 0.95 and rater1 classify 40% of subjects and rate2 classify 50% of subjects as positive. R command used is: N.cohen.kappa(0.40, 0.50, 0.95, 0.81, alpha=0.05, power=0.8, twosided=FALSE ). I am attaching both the 'Excel sheet formula-kappa sample size situation1 & 2'). Why is this so? Please help me to sort this out. Looking forward to hearing from you. Best, Kalaivani -- *Dr. Kalaivani Mani, * *M.Sc., Biostatistics (CMC, Vellore), Ph.D. (AIIMS, Delhi)* *Scientist-IV* *Dept. of Biostatistics* *All India Institute of Medical Sciences* *New Delhi-110029, India.* *Mobile:91-9717319082* ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
