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st: syntax -chi2fit-


From   "Rajiv Mallick" <rmallick@hotmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: syntax -chi2fit-
Date   Thu, 23 Jun 2005 06:11:17 -0500

I am trying to use -chi2fit- test to compare distribution of my variable LOCN against Poisson distribution. I am looking for some guidance on how to use -chi2fit- test, i.e.,
- correct Stata syntax for the test,
- do I need to first compute cdf of the variable,
- in the Stata command how do I specify the theoretical distribution I am comparing the distribution of my variable against,
- do I need to –collapse- the variable? If I do, then is it group wise or for any point.

You can see, any help in implementing this test will be appreciated.

My variable looks and feels like the following, and my attempt on –chi2fit- is below that.


Variable LOCN
----------------------------------------------------------------
. tabulate locn
LOCN | Freq. Percent Cum.
------------+-----------------------------------
0 | 2,984 64.35 64.35
1 | 1,409 30.39 94.74
2 | 185 3.99 98.73
3 | 59 1.27 100.00
------------+-----------------------------------
Total | 4,637 100.00

. summ locn
Variable | Obs Mean Std. Dev. Min Max
-------------+--------------------------------------------------------
locn | 4637 .4218245 .6325427 0 3
----------------------------------------------------------------------


My Attempt on –chi2test-
----------------------------------------------------------------
. chi2fit locn poisson if loyald==1 pw(4) fw(4), bins(4) df(0)
variable poisson not found


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