Date: Tue, 5 Sep 2006 08:46:50 -0700
Reply-To: Dominic Lusinchi <dominic@farwestresearch.com>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: Dominic Lusinchi <dominic@farwestresearch.com>
Organization: Far West Research
Subject: Re: Comparing groups for more n more than 30
In-Reply-To: <9D4BEF69F83C9744AB34E5FE2F78F46DB5E14C@matrix.mrxin.marketrx.com>
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Manmit,
You CAN perform statistical tests with samples less than 30. The issue is:
what is the shape of the parent distribution that has generated the data? If
you can safely assume that it is "normal", you can use any parametric test.
If it is not normal because your sample size is small, the Central Limit
Theorem does not apply, especially if the parent distribution is very
different from a normal distribution. In that case, you can rely on
nonparametric tests.
Anytime a statistical test is used you have to check what assumptions must
be met for it (the test) to be effectively used.
This answers only part of your query. Others on the list more adept with
syntax can help you with the other part: setting a benchmark.
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:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of
Manmit Shrimali
Sent: Monday, September 04, 2006 11:19 PM
To: SPSSX-L@LISTSERV.UGA.EDU
Subject: Comparing groups for more n more than 30
Hello All,
I am facing bit tricky situation. I frequently run statistical
significance testing, column means and column proportions in custom
table. As a rule of thumb, I understand that we should not do
significance testing if n (base) is less than 30. However, SPSS will
still generate the p-values and significance testing even being the
valid n less than 30. Is there any way, to set benchmark for SPSS,
available to set rule of comparing groups and generating stat testing
only if the valid n of groups are more than 30?
Any help will be of great help.
Regards,
Manmit
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