Re: Poisson distribution (rv)

Posted by Art Kendall on Nov 21, 2011; 12:45pm
URL: http://spssx-discussion.165.s1.nabble.com/Poisson-distribution-rv-tp5010174p5010465.html

The arithmetic mean.  A common test to see whether an empirical distribution is poisson is to see if the variance is approximately equal to the mean.

However, for many practical purposes it would not make a difference which you used.
Open a new instance of SPSS.  Paste the syntax below into a syntax window. Run it.

Art Kendall
Social Research Consultants

INPUT PROGRAM.
   LOOP id=1 TO 300000.
      COMPUTE usingmean = rv.poisson( 5.294693).
      COMPUTE usingmedian = rv.poisson( 5).
      END CASE.
   END LOOP.
   END FILE.
END INPUT PROGRAM.
FORMATS id (F3.0) usingmean usingmedian (f3).
FREQUENCIES VARS= usingmean usingmedian/statistics = mean variance.

On 11/21/2011 5:55 AM, drfg2008 wrote:

A question to the Poisson distribution: I would like to generate a poisson
distributed random variable with SPSS (1). I know that the distribution is a
Poisson distribution with the arithmetic mean of 5.294693 and the median of
5. What do I have to give SPSS as "mean": the median or the arithmetic mean.
Or neither. In other words, what is the estimated location parameter in a
Poisson distribution.

Thanks


(1)
COMPUTE rv_poisson=RV.POISSON(xyz).
EXECUTE.

-----
Dr. Frank Gaeth
FU-Berlin

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