[EMAIL PROTECTED] wrote: > Dear list > > I would like to compare two measurements of disease severity (M1 and > M2), one of the is continuous (M1 ranging from 1 to 10) and the other > is ordinal (M2 takes Low, Medium, high and very high). Do you think is > ok to use cor() function to test whether the two agree, i.e correlate? > I am afraid that if I set M2 to 1,2,3 and 4, the function cor() will > take them as continuous and therefore lose intrepretation. > > Thanks for your commments > It's probably not massively wrong, given that the interpretation of correlation coefficients is usually not very clear anyway (excepting maybe nearly-perfect correlated cases). However, a Spearman correlation does have the rather nice feature of being independent of the values you assign to M2, and of any monotone transformation of M1 too.
-- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ 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.
