[R] CI

[Ethan Johnsons]

Thx so much.

I just got into R world for my small research.
I thought that R is free so doesn't have many features, but it seems I
was wrong.

Why do these two return different values?

0.2666456 0.6133544
0.2698531 0.6213784

I think the diff is ignorable, but would ask.

ej

On 10/19/06, Liaw, Andy <andy_liaw at merck.com> wrote:
> You did ask for CI of mean, so that's what you got.  If you want CI for
> proportion, here are two (non-bootstrap) ways:
>
> R> confint(lm(I(x == 1) ~ 1), level=.9)
>                   5 %      95 %
> (Intercept) 0.2666456 0.6133544
> R> binom.test(sum(x == 1), length(x), conf.level=.9)
>
>         Exact binomial test
>
> data:  sum(x == 1) and length(x)
> number of successes = 11, number of trials = 25, p-value = 0.69
> alternative hypothesis: true probability of success is not equal to 0.5
> 90 percent confidence interval:
>  0.2698531 0.6213784
> sample estimates:
> probability of success
>                   0.44
>
> I hope these are not HW problems?
>
> Andy
>
> From: Ethan Johnsons
> >
> > Thank you so much for the feedback.
> >
> > The random numbers are working great.  I have tried
> > non-random numbers, and the outcome is not correct with confint.
> >
> > Is there a way to compute i.e. a 90% confidence interval for
> > percent of 1?
> >
> > i.e. where 1 = apple; 2 = orange
> >
> > > x
> >  [1] 2 2 2 2 2 1 1 2 2 1 2 1 2 2 2 1 1 1 1 1 1 1 2 2 2
> > > table (x)
> > x
> >  1  2
> > 11 14
> >
> > > x =11
> > > confint(lm(x~1), level=0.90)
> >             5 % 95 %
> > (Intercept) NaN  NaN
> >
> > ej
> >
> > On 10/18/06, Liaw, Andy <andy_liaw at merck.com> wrote:
> > > Here's one way:
> > >
> > > R> x <- c(6,11,5,14,30,11,17,3,9,3,8,8) confint(lm(x~1), level=.9)
> > >                  5 %    95 %
> > > (Intercept) 6.546834 14.2865
> > >
> > > Andy
> > >
> > > From: Ethan Johnsons
> > > >
> > > > I have a quick question, please.
> > > >
> > > > Does R have function to compute i.e. a 90% confidence
> > interval for
> > > > the mean for these numbers?
> > > >
> > > > > mean (6,11,5,14,30,11,17,3,9,3,8,8)
> > > > [1] 6
> > > >
> > > > I thought pt or qt would give me the interval, but it seems not.
> > > >
> > > > thx much.
> > > >
> > > > ej
> > > >
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