Re: [R] Polychoric and tetrachoric correlation
Dear John, Yes, that's great - thanks! Andy John Fox wrote: Dear Andy, Yes, the tetrachoric correlation is a special case of the polychoric correlation when both factors are dichotomous. The 95-percent confidence interval that you suggest might be adequate if the sample size is sufficiently large and the correlation isn't too close to 0 or 1, but it is probably not in general terribly trustworthy. I hope this helps, John Original message: Andy Fugard a.fugard at ed.ac.uk Mon Sep 1 19:25:54 CEST 2008 Hi there, Am I correct to believe that tetrachoric correlation is a special case of polychoric correlation when there are only two levels to the ordered factor? Thus it should be okay to use hetcor from the polycor package to build a matrix of correlations for binary variables? If this is true, how can one estimate 95% confidence intervals for the correlations? My guess would be mat = hetcor(dataframe) mat$correlation - (1.96 * mat$std.errors) mat$correlation + (1.96 * mat$std.errors) Thanks, Andy -- Andy Fugard, Postgraduate Research Student Psychology (Room S6), The University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK +44 (0)78 123 87190 http://figuraleffect.googlepages.com/ The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. __ R-help@r-project.org 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] Polychoric and tetrachoric correlation
Dear Andy, Yes, the tetrachoric correlation is a special case of the polychoric correlation when both factors are dichotomous. The 95-percent confidence interval that you suggest might be adequate if the sample size is sufficiently large and the correlation isn't too close to 0 or 1, but it is probably not in general terribly trustworthy. I hope this helps, John Original message: Andy Fugard a.fugard at ed.ac.uk Mon Sep 1 19:25:54 CEST 2008 Hi there, Am I correct to believe that tetrachoric correlation is a special case of polychoric correlation when there are only two levels to the ordered factor? Thus it should be okay to use hetcor from the polycor package to build a matrix of correlations for binary variables? If this is true, how can one estimate 95% confidence intervals for the correlations? My guess would be mat = hetcor(dataframe) mat$correlation - (1.96 * mat$std.errors) mat$correlation + (1.96 * mat$std.errors) Thanks, Andy -- Andy Fugard, Postgraduate Research Student Psychology (Room S6), The University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK +44 (0)78 123 87190 http://figuraleffect.googlepages.com/ The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. -- John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario, Canada web: socserv.mcmaster.ca/jfox __ R-help@r-project.org 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] Polychoric and tetrachoric correlation
Hi there, Am I correct to believe that tetrachoric correlation is a special case of polychoric correlation when there are only two levels to the ordered factor? Thus it should be okay to use hetcor from the polycor package to build a matrix of correlations for binary variables? If this is true, how can one estimate 95% confidence intervals for the correlations? My guess would be mat = hetcor(dataframe) mat$correlation - (1.96 * mat$std.errors) mat$correlation + (1.96 * mat$std.errors) Thanks, Andy -- Andy Fugard, Postgraduate Research Student Psychology (Room S6), The University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK +44 (0)78 123 87190 http://figuraleffect.googlepages.com/ The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. __ R-help@r-project.org 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.
