Posted by
Margaret MacDougall on
Sep 05, 2006; 5:56pm
URL: http://spssx-discussion.165.s1.nabble.com/Query-re-authenticity-of-p-values-for-chi-square-goodness-of-fit-test-tp1070734p1070736.html
Dear Dominic
Thank you for your kind reply. However, I do not wish to collapse categories and I am already assuming a multnomial distribution. What I really need to know is whether it is sound to use the chi-square goodness-of-fit test when the expected count is less than 5 and indeed why SPSS chooses to specifically flag the result that the expected count is less than 5 when there does not appear to be an alternative test for the one-dimensional case to which one can resort in such cases.
Best wishes
Margaret
Dominic Lusinchi <
[hidden email]> wrote:
Margaret,
I don't see that anybody replied to your query.
You have two options (apart from collecting more data, but we will ignore
that): collapse categories, or use the multinomial distribution, which is
the extension of the binomial when there are more than 2 outcomes. There may
be syntax on Ray's site to compute it, but I don't know.
To see the formula for the multinomial go to
http://en.wikipedia.org/wiki/Multinomial_distributionyou will see how closely it relates to the binomial.
Sorry I can't be more specific than that.
Good luck,
Dominic
Dominic Lusinchi
Statistician
Far West Research
Statistical Consulting
San Francisco, California
415-664-3032
www.farwestresearch.com
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of
Margaret MacDougall
Sent: Tuesday, September 05, 2006 3:02 AM
To:
[hidden email]
Subject: Query re authenticity of p-values for chi-square goodness of fit
test
Hello
I would be most grateful for some advice on whether or not to accept the
p-value obtained from running the chi-square goodness-of-fit test in SPSS
when the expected count is less than 5. I am familiar with the golden rule
for when to use Fisher's Exact test for cross-tabulated data but what should
one do in the one-dimensional case? When the expected count is less than 5,
a p-value is generated by SPSS but this is accompanied by a footnote
indicating that all expected counts are less than 5 (with no advice as to
why this is important to know).
Many thanks for your interest
Best wishes
Margaret
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