[R] CI with sd

[Ethan Johnsons]

Thank you so much.
I see your point.

ej

On 10/20/06, Petr Pikal <petr.pikal at precheza.cz> wrote:
> Hi
>
> On 19 Oct 2006 at 13:19, Ethan Johnsons wrote:
>
> Date sent:              Thu, 19 Oct 2006 13:19:40 -0400
> From:                   "Ethan Johnsons" <ethan.johnsons at gmail.com>
> To:                     "Chuck Cleland" <ccleland at optonline.net>
> Copies to:              r-help at stat.math.ethz.ch
> Subject:                Re: [R] CI with sd
>
> > I thought of another interesting scenario, and I would just go ahead
> > and ask this. I have a mean (i.e. 26.2) where the number of e coli
> > samples is 250. The mean is already calculated, so it is a discrete
> > value, not series.
> >
> > What fucntion can be used for the calc with CI i.e. 90%?
>
> With some sd value and assuming normal distribution
>
> 26.2+qnorm(.95)*sd/sqrt(250)
> 26.2-qnorm(.95)*sd/sqrt(250)
>
> as you can find in statistical textbooks.
>
> But without having sd value?
>
> HTH
> Petr
>
>
> >
> > thx much,
> >
> > ej
> >
> > On 10/19/06, Chuck Cleland <ccleland at optonline.net> wrote:
> > > Ethan Johnsons wrote:
> > > > Please let me ask you another quick question.
> > > > I have results for e coli, and am trying to get 95% CI with the sd
> > > > (1.783956). I got the result from another tool as (1.21, 3.42).
> > > > But, I like to verify it with R.  What function do you use for
> > > > this?
> > > >
> > > >> e.coli=c(27.5,24.6,25.3,28.7,23,26.8,24.7,24.3,24.9)
> > > >> sd(e.coli, na.rm = FALSE)
> > > > [1] 1.783956
> > > >
> > > > Sorry for the newbie question.
> > >
> > > e.coli <- c(27.5,24.6,25.3,28.7,23,26.8,24.7,24.3,24.9)
> > > library(nlme)
> > > mod1 <- gls(e.coli ~ 1)
> > > intervals(mod1)
> > >
> > > Approximate 95% confidence intervals
> > >
> > >  Coefficients:
> > >                lower     est.    upper
> > > (Intercept) 24.16206 25.53333 26.90460
> > > attr(,"label")
> > > [1] "Coefficients:"
> > >
> > >  Residual standard error:
> > >    lower     est.    upper
> > > 1.204986 1.783956 3.417651
> > >
> > > > thx much
> > > >
> > > > ej
> > > >
> > > > ______________________________________________
> > > > R-help at stat.math.ethz.ch mailing list
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> > >
> > > --
> > > Chuck Cleland, Ph.D.
> > > NDRI, Inc.
> > > 71 West 23rd Street, 8th floor
> > > New York, NY 10010
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> > >
> > >
> >
> > ______________________________________________
> > 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 and provide commented,
> > minimal, self-contained, reproducible code.
>
> Petr Pikal
> petr.pikal at precheza.cz
>
>