Re: [R] how to test poisson distribution

From: Achim Zeileis <Achim.Zeileis_at_wu-wien.ac.at>
Date: Thu 20 Oct 2005 - 03:31:26 EST

On Wed, 19 Oct 2005 10:18:02 -0700 Berton Gunter wrote:

> To be pedantic (I'm feeling cranky today):
>
> One can never test "whether the data follow ["data" is plural] a
> Poisson distribution" -- only whether there is sufficient evidence to
> cast that assumption into doubt. Perhaps a better shorthand is
> "whether the data are consistent with Poisonness" . This correctly
> leaves open the possibility that the data are consistent with lots of
> other distribution-nesses, too. I welcome alternatives, perhaps
> privately to reduce the list noise level.

...now that Berton mentioned `checking distribution-nesses': the function distplot() in the package vcd implements various plots for distribution-nesses that can be used for graphical checking. Ord_plot() is made for a similar purpose.
Finally, there is also a function goodfit() that computes goodness-of-fit tests for such hypotheses.

All three functions are written following Chapter 2 `Fitting and Graphing Discrete Distributions' in Michael Friendly's book `Visualizing Categorical Data'.

hth,
Z

> (And,yes, I'm sure that Thomas knows this perfectly well).
>
> I do think that we should be a bit less sloppy about such things even
> here, lest we continue to promulgate already widespread
> misunderstandings, even at the cost of slightly increased bandwidth.
> After all, precision is supposed to be a major concern or ours.

>
> As I've been cranky, others are free to return the favor. Sauce for
> the goose ...
>
> -- Bert Gunter
> Genentech Non-Clinical Statistics
> South San Francisco, CA
>
> "The business of the statistician is to catalyze the scientific
> learning process." - George E. P. Box
>
>
>
> > -----Original Message-----
> > From: r-help-bounces@stat.math.ethz.ch
> > [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Thomas
> > Schönhoff
> > Sent: Wednesday, October 19, 2005 10:00 AM
> > To: r-help@stat.math.ethz.ch
> > Subject: Re: [R] how to test poisson distribution
> >
> > Hi,
> >
> >
> > 2005/10/19, Wensui Liu <liuwensui@gmail.com>:
> > > Dear All,
> > >
> > > I am wonderng how to test whether the data follows poisson
> > distribution.
> > >
> > > Thank you so much!
> >
> > Did you notice the PDF on distribution tests using R by Vito Ricci,
> > its found at CRAN in the docs contrib section, called "FITTING
> > DISTRIBUTIONS WITH R"
> >
> > Maybe this could be of some help for you, especially look at page 7
> > (poisson dsitribution example).
> >
> > ______________________________________________
> > R-help@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
> >
>
> ______________________________________________
> R-help@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
>



R-help@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 Received on Thu Oct 20 03:35:51 2005

This archive was generated by hypermail 2.1.8 : Sun 23 Oct 2005 - 19:06:59 EST