Bert Gunter
2022-Jun-16 16:29 UTC
[R] Fwd: Query regarding R 'irr' package 'N.cohen.kappa'
---------- Forwarded message --------- From: Bert Gunter <bgunter.4567 at gmail.com> Date: Thu, Jun 16, 2022 at 9:28 AM Subject: Re: [R] Query regarding R 'irr' package 'N.cohen.kappa' To: Kalaivani Mani <manikalaivani at gmail.com> Please read and follow the posting guide (linked below). No attachments came through, because most attachments are stripped due to security concerns. The PG tells you which attachments are allowed. We don't do Excel here. This is R-help. Do and show your manual calculations in R. Cheers, Bert On Thu, Jun 16, 2022 at 9:20 AM Kalaivani Mani <manikalaivani at gmail.com> wrote:> 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 at 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. >[[alternative HTML version deleted]]