Dear List! I want to compare medians of non normal distributed data. Is it possible and usefull to calculate 95% confidence intervals for medians? And if so - how can this be achieved in R? Thanks a lot! Anna -- Der Inhalt dieser E-Mail ist vertraulich. Sollte Ihnen die E-Mail irrt?mlich zugesandt worden sein, bitte ich Sie, mich unverz?glich zu benachrichtigen und die E-Mail zu l?schen. This e-mail is confidential. If you have received it in error, please notify me immediately and delete it from your system.
The default rank test in the quantreg package would look like this summary(rq(y ~ d, tau = .5)) where d is a factor variable indicating which sample the elements of y belonged to. Summary returns a confidence interval for the coef of the factor variable -- if this interval excludes zero at the chosen alpha level then the difference in medians is "significant." Roger Koenker rkoenker at illinois.edu On Mar 31, 2011, at 4:15 AM, Anna Lee wrote:> Dear List! > > I want to compare medians of non normal distributed data. Is it > possible and usefull to calculate 95% confidence intervals for > medians? And if so - how can this be achieved in R? > > Thanks a lot! > Anna > > -- > > > > Der Inhalt dieser E-Mail ist vertraulich. Sollte Ihnen die E-Mail > irrt?mlich zugesandt worden sein, bitte ich Sie, mich unverz?glich zu > benachrichtigen und die E-Mail zu l?schen. > > This e-mail is confidential. If you have received it in error, please > notify me immediately and delete it from your system. > > ______________________________________________ > R-help at 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.
You could do bootstrapping for confidence intervals or permutation tests for just comparing the medians. There are other tools as well, just be sure that you understand what you are testing and what assumptions are being made in whatever method you choose. -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.snow at imail.org 801.408.8111> -----Original Message----- > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r- > project.org] On Behalf Of Anna Lee > Sent: Thursday, March 31, 2011 3:15 AM > To: r-help at r-project.org > Subject: [R] statistical question > > Dear List! > > I want to compare medians of non normal distributed data. Is it > possible and usefull to calculate 95% confidence intervals for > medians? And if so - how can this be achieved in R? > > Thanks a lot! > Anna > > -- > > > > Der Inhalt dieser E-Mail ist vertraulich. Sollte Ihnen die E-Mail > irrt?mlich zugesandt worden sein, bitte ich Sie, mich unverz?glich zu > benachrichtigen und die E-Mail zu l?schen. > > This e-mail is confidential. If you have received it in error, please > notify me immediately and delete it from your system. > > ______________________________________________ > R-help at 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.