Many many thanks for the input in this context.

Nico

On Thu, Oct 4, 2012 at 4:56 PM, Jose Iparraguirre <
Jose.Iparraguirre@ageuk.org.uk> wrote:

> Hi,
>
> You can also have a look at this paper (no subscription needed):
>
> Herberich, E.; Sikorski, J.; and Hothorn, T. (2010). "A Robust Procedure
> for Comparing Multiple Means under Heteroscedasticity in Unbalanced
> Designs". PLoSONE, Vol. 5, Issue 3, e9788. doi:10.1371/journal.pone.0009788
>
> In this paper, Herberich et al have included a piece of R code to run
> their procedure. Their procedure is a modification of Tukey, and as it says
> in the title of the paper, it can be used regardless of whether the samples
> had different sizes or distributions.
>
> José
>
>
> José Iparraguirre
> Chief Economist
> Age UK
>
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> E Jose.Iparraguirre@ageuk.org.uk
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>
> -----Original Message-----
> From: r-help-bounces@r-project.org [mailto:r-help-bounces@r-project.org]
> On Behalf Of arun
> Sent: 04 October 2012 13:59
> To: John Kane
> Cc: R help
> Subject: Re: [R] t-test
>
> Hi John,
> You are right.  With more than two groups, the type 1 error rate should be
> a problem.
> A.K.
>
>
>
> ----- Original Message -----
> From: John Kane <jrkrideau@inbox.com>
> To: arun <smartpink111@yahoo.com>
> Cc:
> Sent: Thursday, October 4, 2012 8:40 AM
> Subject: Re: [R] t-test
>
> My stats are lousy but isnt Nico doing some multiple t-tests when an anova
> with some post hoc comparisons complete with a Tukey or Bonferroni
> correction looks more suitable?
>
> Of course I have no idea of the topic area and maybe he has already done
> thi.
>
> John Kane
> Kingston ON Canada
>
>
> > -----Original Message-----
> > From: smartpink111@yahoo.com
> > Sent: Thu, 4 Oct 2012 05:31:55 -0700 (PDT)
> > To: nicomet80@gmail.com
> > Subject: Re: [R] t-test
> >
> > HI,
> > Try this:
> > sapply(split(dat,dat$Name),function(x) t.test(x[,2],dat[,2])$p.value)
> > #    CTK100     CTK103     CTK121
> > #0.86330310 0.32706859 0.02023357
> > A.K.
> >
> >
> >
> > ----- Original Message -----
> > From: Nico Met <nicomet80@gmail.com>
> > To: Rui Barradas <ruipbarradas@sapo.pt>
> > Cc: r-help@r-project.org; r-help <r-help@stat.math.ethz.ch>
> > Sent: Thursday, October 4, 2012 6:37 AM
> > Subject: Re: [R] t-test
> >
> > Dear Rui,
> >
> > Many thanks for help.
> >
> > "mean for CTK and all"  = comparison between mean of all groups ( which
> > means second col) vs. each groups like CTK100, CTK121 etc.
> >
> > Regards
> >
> > Nico
> >
> > On Thu, Oct 4, 2012 at 12:28 PM, Rui Barradas <ruipbarradas@sapo.pt>
> > wrote:
> >
> >> Hello,
> >>
> >> I'm not quite sure I understand, but something like this?
> >>
> >> tapply(dat$Score, dat$Name, FUN = mean)
> >> sapply(unique(dat$Name), function(un){
> > >     with(dat, t.test(Score[Name == un], Score[Name != un])$p.value)})
> >>
> >> My doubt is in what you mean by "mean for CTK and all". The ?t.test
> >> gives
> >> a confidence interval for the difference in the means, so maybe you'll
> >> have
> >> to look there for what you want.
> >>
> >> Hope this helps,
> >>
> >> Rui Barradas
> >> Em 04-10-2012 10:34, Nico Met escreveu:
> >>
> >>> Dear Group,
> >>>
> >>> I want to do a t-test calculation on a large data set.
> >>>
> >>> I am pasting some part of it
> >>>
> >>> structure(list(Name = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 3L,
> >>> 3L, 3L, 3L, 3L, 3L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
> >>> 2L), .Label = c("CTK100", "CTK103", "CTK121"), class = "factor"),
> > >>      Score = c(236.9726, 207.0055, 237.3464, 224.4774, 236.5034,
> > >>      206.7382, 233.94, 240.31, 240.9, 235.15, 223.36, 248.67,
> > >>      249.25, 201.4051, 244.1689, 182.2756, 229.001, 241.3211,
> > >>      196.0453, 232.6055, 225.0783, 196.0453, 232.6055, 225.0783
> > >>      )), .Names = c("Name", "Score"), class = "data.frame", row.names
> > =
> >>> c(NA,
> >>> 24L))
> >>>
> >>>
> >>> I want to compare groups with CTK100 and with all the groups and want
> >>> to
> >>> save the p-values and mean for each of that particular group (for
> >>> example:
> >>> mean for CTK and all)
> >>> Similarly, for other groups like that CTK121 etc...
> >>>
> >>> Is there any way to automate this process?
> >>>
> >>> Thanks for your advice !!!!!
> >>>
> >>> Nico
> >>>
> > >>         [[alternative HTML version deleted]]
> >>>
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> >>
> >>
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