Re: [R] Cohen's Kappa
...many thanks for all the answers and clarity!!! regards, christian Hi, Chance is not .5 in your data, it's a function of the expected values for presence and absence: (((7792*10855)/11974) + ((4182*1119)/11974))/11974 [1] 0.6225686 (.6862368-.6225686)/(1-.6225686) [1] 0.1686881 Scot On Thu, 22 Mar 2007, Christian Schulz wrote: Hi, im little bit confused about Cohen's Kappa and i should be look into the Kappa function code. Is the easy formula really wrong? kappa=agreement-chance/(1-chance) many thanks christian ### true-negativ:7445 false-positive:3410 false-negativ:347 true-positiv:772 classification-aggrement:68,6% kappa=agreement-chance/(1-chance) = (0.686-0.5)/0.5=0.372 .with function from library(vcd) Kappa(matrix(c(7445,3410,347,772),nrow=2)) value ASE Unweighted 0.1686882 0.011235188 Weighted 0.1686882 0.007979293 __ R-help@stat.math.ethz.ch mailing list 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. -- Scot W. McNary email: smcnaryatcharmdotnet __ R-help@stat.math.ethz.ch mailing list 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. __ R-help@stat.math.ethz.ch mailing list 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.
Re: [R] Cohen's Kappa
See also section 6.4 of http://www.psych.upenn.edu/~baron/rpsych/rpsych.html which also points to a few packages that have kappa code in them. -- Jonathan Baron, Professor of Psychology, University of Pennsylvania Home page: http://www.sas.upenn.edu/~baron __ R-help@stat.math.ethz.ch mailing list 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.
[R] Cohen's Kappa
Hi, im little bit confused about Cohen's Kappa and i should be look into the Kappa function code. Is the easy formula really wrong? kappa=agreement-chance/(1-chance) many thanks christian ### true-negativ:7445 false-positive:3410 false-negativ:347 true-positiv:772 classification-aggrement:68,6% kappa=agreement-chance/(1-chance) = (0.686-0.5)/0.5=0.372 .with function from library(vcd) Kappa(matrix(c(7445,3410,347,772),nrow=2)) value ASE Unweighted 0.1686882 0.011235188 Weighted 0.1686882 0.007979293 __ R-help@stat.math.ethz.ch mailing list 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.
Re: [R] Cohen's Kappa
Shouldn't that be kappa = rater1 - rater2 / (1-chance) ? Andy -- Andrew J Perrin - andrew_perrin (at) unc.edu - http://perrin.socsci.unc.edu Assistant Professor of Sociology; Book Review Editor, _Social Forces_ University of North Carolina - CB#3210, Chapel Hill, NC 27599-3210 USA New Book: http://www.press.uchicago.edu/cgi-bin/hfs.cgi/00/178592.ctl On Thu, 22 Mar 2007, Christian Schulz wrote: Hi, im little bit confused about Cohen's Kappa and i should be look into the Kappa function code. Is the easy formula really wrong? kappa=agreement-chance/(1-chance) many thanks christian ### true-negativ:7445 false-positive:3410 false-negativ:347 true-positiv:772 classification-aggrement:68,6% kappa=agreement-chance/(1-chance) = (0.686-0.5)/0.5=0.372 .with function from library(vcd) Kappa(matrix(c(7445,3410,347,772),nrow=2)) value ASE Unweighted 0.1686882 0.011235188 Weighted 0.1686882 0.007979293 __ R-help@stat.math.ethz.ch mailing list 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. __ R-help@stat.math.ethz.ch mailing list 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.
Re: [R] Cohen's Kappa
Hi, Chance is not .5 in your data, it's a function of the expected values for presence and absence: (((7792*10855)/11974) + ((4182*1119)/11974))/11974 [1] 0.6225686 (.6862368-.6225686)/(1-.6225686) [1] 0.1686881 Scot On Thu, 22 Mar 2007, Christian Schulz wrote: Hi, im little bit confused about Cohen's Kappa and i should be look into the Kappa function code. Is the easy formula really wrong? kappa=agreement-chance/(1-chance) many thanks christian ### true-negativ:7445 false-positive:3410 false-negativ:347 true-positiv:772 classification-aggrement:68,6% kappa=agreement-chance/(1-chance) = (0.686-0.5)/0.5=0.372 .with function from library(vcd) Kappa(matrix(c(7445,3410,347,772),nrow=2)) value ASE Unweighted 0.1686882 0.011235188 Weighted 0.1686882 0.007979293 __ R-help@stat.math.ethz.ch mailing list 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. -- Scot W. McNary email: smcnaryatcharmdotnet __ R-help@stat.math.ethz.ch mailing list 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.
Re: [R] Cohen's Kappa
Cohen, J. (1960). A coefficient of agreement for nominal scales. Educational and Psychological Measurement, 20, 37-46. Cohen, J. (1968). Weighted kappa: Nominal scale agreement with provision for scaled disagreement or partial credit. Psychological Bulletin, 70, 213-220. Francisco Dr. Francisco J. Zagmutt College of Veterinary Medicine and Biomedical Sciences Colorado State University Christian Schulz wrote: Hi, im little bit confused about Cohen's Kappa and i should be look into the Kappa function code. Is the easy formula really wrong? kappa=agreement-chance/(1-chance) many thanks christian ### true-negativ:7445 false-positive:3410 false-negativ:347 true-positiv:772 classification-aggrement:68,6% kappa=agreement-chance/(1-chance) = (0.686-0.5)/0.5=0.372 ..with function from library(vcd) Kappa(matrix(c(7445,3410,347,772),nrow=2)) value ASE Unweighted 0.1686882 0.011235188 Weighted 0.1686882 0.007979293 __ R-help@stat.math.ethz.ch mailing list 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. __ R-help@stat.math.ethz.ch mailing list 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.
