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st: question on goodness of fit tests

From   "Narasimhan Sowmyanarayanan" <>
Subject   st: question on goodness of fit tests
Date   Thu, 13 Jul 2006 10:15:23 -0400

Hello folks:

I am facing a small confusion that I have not been able to resolve. I
am trying to fit a beta geometric distribution to my dataset. I tried
the standard chi square goodness of fit test and this is rejected in
my data. (chi square = 122 and df = 34).

However an examination of the correlation between the two series shows
a correlation of .9995 and I actually tried superimposing a plot of
the observed and the expected values. The values are extremely close.

I tried something that may not be entirely right in this context but
just out of curiosity. I used the kolmogorov-Smirnov test by treating
the observed and the expected values as different groups and the test
indicated that the distributions were not different between the
observed and the expected values .

Two-sample Kolmogorov-Smirnov test for equality of distribution functions:

Smaller group       D       P-value      Exact
0:                  0.2059    0.237
1:                 -0.0882    0.767
Combined K-S:       0.2059    0.467      0.307

Can someone suggest a way forward. Is it correct to assume that the
model fits the data ?

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