[R] Homework help: Is this how CIs of normal distributionsare computed?
Zembower, Kevin
kzembowe at jhuccp.org
Wed Oct 31 21:17:50 CET 2007
Daniel, thanks, I should have remembered this, too; I've seen it and
worked with it before. Thanks.
-Kevin
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Daniel Lakeland
Sent: Wednesday, October 31, 2007 4:04 PM
To: r-help at r-project.org
Subject: Re: [R] Homework help: Is this how CIs of normal
distributionsare computed?
On Wed, Oct 31, 2007 at 03:56:37PM -0400, Zembower, Kevin wrote:
> I'm looking for a function in R similar to t.test() which was
generously
> pointed out to me yesterday, but which can be used for normally
> distributed data.
...
> > x100<-sample(x, 100, replace=TRUE)
>
> I think that I should be able to use a normal distribution, because of
> the n>30 rule-of-thumb.
>
> I can compute the 95% CI using:
> > mean(x100) - qnorm(alpha/2)*sd(x100)/sqrt(length(x100))
You can compute quantiles of the particular normal distribution itself
rather than transforming from the standardized normal by hand.
qnorm(c(.025,.975),mean=mean(x100),sd=sd(x100)/sqrt(length(x100)))
--
Daniel Lakeland
dlakelan at street-artists.org
http://www.street-artists.org/~dlakelan
______________________________________________
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.
More information about the R-help
mailing list