[R] how to test poisson distribution

[Achim Zeileis]

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 at stat.math.ethz.ch 
> > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Thomas 
> > Schönhoff
> > Sent: Wednesday, October 19, 2005 10:00 AM
> > To: r-help at stat.math.ethz.ch
> > Subject: Re: [R] how to test poisson distribution
> > 
> > Hi,
> > 
> > 
> > 2005/10/19, Wensui Liu <liuwensui at 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).
> > 
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