wow, thanks for the informative inputs! I'm glad I post that silly
question..thanks!

On Wed, Oct 17, 2012 at 6:51 PM, Greg Snow <538280@gmail.com> wrote:

> Rui answered the main question by pointing out that you need z.test(m,
> stdev=s(m)), or you could use z.test(m,,sd(m)), but I think the stdev=
> approach is clearer.  But you are really abusing the concept of z
> tests in general (and the z.test function in particular) by using the
> sd of the sample.  If you use the sd of the sample then you should be
> doing a t test (and the t.test function does this simpler than the
> z.test function).  The z.test function was designed to use in classes
> that introduce the concepts of inference using the generally
> unrealistic (but simpler) case of knowing the population standard
> deviation, but not the mean.  The z.test function was to be a bridge
> so that the students could use a function that was similar to the
> t.test function that they would eventually use.
>
> On Wed, Oct 17, 2012 at 12:45 AM, Balqis <aehan3616@gmail.com> wrote:
> > Hi!
> > I'm trying to use sapply to my dataframe for z.test function (teaching
> > demos package)
> >
> >
> > Sep=cbind(kIp,k02p,k04p,k07p)
> > Sep=as.data.frame(Sep)
> >
> > kzt=sapply(Sep, function(m) z.test(m,sd(m)))
> > Error in z.test(m, sd(Sep)) :
> >   You must specify a Standard Deviation of the population
> >
> > kzt=sapply(Sep, function(m) z.test(m,sd(Sep)))
> > Error in z.test(m, sd(Sep)) :
> >   You must specify a Standard Deviation of the population
> >
> > #obviously it can't process the z.test because of the sd function
> embedded
> > inside the function. can someone point me how to fix this. Many thanks!
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@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.
>
>
>
> --
> Gregory (Greg) L. Snow Ph.D.
> 538280@gmail.com
>

	[[alternative HTML version deleted]]


