Hi R-people, I am wanting to run Factorial ANOVA followed by Scheffe tests on some spatial subjective data. I'm comparing X-Y independent coordinates against x-y dependent coordinates. There are only four independent spatial coordinates that form a square. I am wondering whether I am doing the right thing, because there doesn't seem to be a simple way of doing this. I have attempted to read `Practical regression and ANOVA using R' and am still confused. In good ol' Statview (now dearly departed) to complete a Scheffe test you selected the independent variables and dependent variable and it produced a table with the pairwise comparisons of the levels of the factor. I'm looking for a system that is as basic, but can be done using R and has documentation so I'm not guessing what I'm doing. I'd rather not have to do plots in R and then run over to dead software to do Scheffe's if possible. I checked on google and there seems to be code for a couple of functions out there, but I need something that has a manual. Is there a Scheffe function out there that is reasonably well documented, or should I consider some other method of dealing with this data. We have been using Scheffe for this type of analysis as I was under the impression it was very conservative. Tukey's HSD seems to be conservative as well. Should I try this? Is there a different approacch that is better and where can I read about it. Thanks for any help you can provide. Sam
Hi, I don't think there are any packages on CRAN that implement Scheffe's test. If you don't mind using another multiple comparisons procedure, you could look at ?TukeyHSD and/or the multcomp package. Alternatively, you could write your own function to do Scheffe's test. At least one other person has done that. See the following post in the R-help archive http://finzi.psych.upenn.edu/R/Rhelp02a/archive/19393.html. I can't vouch for whether that person's function works properly, but it shouldn't be hard to hand-check it, and improve it. You could search R-help yourself and maybe come up with other solutions. Cheers, Simon.>Hi R-people, > >I am wanting to run Factorial ANOVA followed by Scheffe tests on >some spatial subjective data. I'm comparing X-Y independent >coordinates against x-y dependent coordinates. There are only four >independent spatial coordinates that form a square. > >I am wondering whether I am doing the right thing, because there >doesn't seem to be a simple way of doing this. I have attempted to >read `Practical regression and ANOVA using R' and am still confused. > >In good ol' Statview (now dearly departed) to complete a Scheffe >test you selected the independent variables and dependent variable >and it produced a table with the pairwise comparisons of the levels >of the factor. I'm looking for a system that is as basic, but can be >done using R and has documentation so I'm not guessing what I'm >doing. I'd rather not have to do plots in R and then run over to >dead software to do Scheffe's if possible. > >I checked on google and there seems to be code for a couple of >functions out there, but I need something that has a manual. > >Is there a Scheffe function out there that is reasonably well >documented, or should I consider some other method of dealing with >this data. We have been using Scheffe for this type of analysis as I >was under the impression it was very conservative. Tukey's HSD seems >to be conservative as well. Should I try this? Is there a different >approacch that is better and where can I read about it. > >Thanks for any help you can provide. > >Sam > >______________________________________________ >R-help at 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-- Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat. Visiting Fellow School of Botany & Zoology The Australian National University Canberra ACT 0200 Australia T: +61 2 6125 8057 email: Simon.Blomberg at anu.edu.au F: +61 2 6125 5573 CRICOS Provider # 00120C
I stand corrected, although confidence.ellipse is a plotting function, and may not be quite what the questioner had in mind. Cheers, Simon.>See confidence.ellipse() in the car() package. (Found from an R site search >on "Scheffe") > >-- Bert Gunter >Genentech Non-Clinical Statistics >South San Francisco, CA > >"The business of the statistician is to catalyze the scientific learning >process." - George E. P. Box > > > >> -----Original Message----- >> From: r-help-bounces at stat.math.ethz.ch >> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Simon Blomberg >> Sent: Tuesday, March 01, 2005 4:25 PM >> To: samferguson at ihug.com.au; R-help at stat.math.ethz.ch >> Subject: Re: [R] Anova with Scheffe Tests >> >> Hi, >> >> I don't think there are any packages on CRAN that implement Scheffe's >> test. If you don't mind using another multiple comparisons procedure, >> you could look at ?TukeyHSD and/or the multcomp package. >> Alternatively, you could write your own function to do Scheffe's >> test. At least one other person has done that. See the following post >> in the R-help archive >> http://finzi.psych.upenn.edu/R/Rhelp02a/archive/19393.html. I can't >> vouch for whether that person's function works properly, but it >> shouldn't be hard to hand-check it, and improve it. You could search >> R-help yourself and maybe come up with other solutions. >> >> Cheers, >> >> Simon. >> >> >Hi R-people, >> > >> >I am wanting to run Factorial ANOVA followed by Scheffe tests on >> >some spatial subjective data. I'm comparing X-Y independent >> >coordinates against x-y dependent coordinates. There are only four >> >independent spatial coordinates that form a square. >> > >> >I am wondering whether I am doing the right thing, because there >> >doesn't seem to be a simple way of doing this. I have attempted to >> >read `Practical regression and ANOVA using R' and am still confused. >> > >> >In good ol' Statview (now dearly departed) to complete a Scheffe >> >test you selected the independent variables and dependent variable >> >and it produced a table with the pairwise comparisons of the levels >> >of the factor. I'm looking for a system that is as basic, but can be >> >done using R and has documentation so I'm not guessing what I'm >> >doing. I'd rather not have to do plots in R and then run over to >> >dead software to do Scheffe's if possible. >> > >> >I checked on google and there seems to be code for a couple of >> >functions out there, but I need something that has a manual. >> > >> >Is there a Scheffe function out there that is reasonably well >> >documented, or should I consider some other method of dealing with >> >this data. We have been using Scheffe for this type of analysis as I >> >was under the impression it was very conservative. Tukey's HSD seems >> >to be conservative as well. Should I try this? Is there a different >> >approacch that is better and where can I read about it. >> > >> >Thanks for any help you can provide. >> > >> >Sam >> > >> >______________________________________________ >> >R-help at 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 >> >> >> -- >> Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat. >> Visiting Fellow >> School of Botany & Zoology >> The Australian National University >> Canberra ACT 0200 >> Australia >> >> T: +61 2 6125 8057 email: Simon.Blomberg at anu.edu.au >> F: +61 2 6125 5573 >> >> CRICOS Provider # 00120C >> >> ______________________________________________ >> R-help at 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 >>-- Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat. Visiting Fellow School of Botany & Zoology The Australian National University Canberra ACT 0200 Australia T: +61 2 6125 8057 email: Simon.Blomberg at anu.edu.au F: +61 2 6125 5573 CRICOS Provider # 00120C
> >In good ol' Statview (now dearly departed) to complete a Scheffe >test you selected the independent variables and dependent variable >and it produced a table with the pairwise comparisons of the levels >of the factor. I'm looking for a system that is as basic, but can be >done using R and has documentation so I'm not guessing what I'm >doing. I'd rather not have to do plots in R and then run over to >dead software to do Scheffe's if possible. > >I checked on google and there seems to be code for a couple of >functions out there, but I need something that has a manual. > >Is there a Scheffe function out there that is reasonably well >documented, or should I consider some other method of dealing with >this data. We have been using Scheffe for this type of analysis as I >was under the impression it was very conservative. Tukey's HSD seems >to be conservative as well. Should I try this? Is there a different >approacch that is better and where can I read about it. > >Thanks for any help you can provide. > >Sam >It sounds like you are only interested in simple pairwise comparisons, in which case you are better off using Tukey's HSD. This will still protect the family-wise error rate, but will allow you to infer more differences than you would using Scheff?'s method. Scheff?'s method is exact if you are truly interested in all contrasts (a situation I have never come across), but it is overly conservative when inferences are only made for pairwise differences. A geometric explanation of the difference between the two methods can be found in Jason Hsu's book "Multiple Comparisons: Theory and Methods". As you can also read in that book, there is no good reason to precede Tukey's HSD with an ANOVA F-test. Tukey's HSD controls the family-wise error rate anyway, so an initial F-test is superfluous. --Jim James A. Rogers Manager, Nonclinical Statistics PGR&D Groton Labs Eastern Point Road (MS 8260-1331) Groton, CT 06340 office: (860) 686-0786 fax: (860) 715-5445 LEGAL NOTICE\ Unless expressly stated otherwise, this messag...{{dropped}}