Date: Wed, 19 Apr 2006 09:53:49 -0300
Reply-To: Hector Maletta <email@example.com>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: Hector Maletta <firstname.lastname@example.org>
Subject: Re: Minimum number of cases for computing correlation
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There is no simple answer to your 'simple' question. Consider the following
1. Regression may involve any number of variables. An old rule of thumb, not
very well justified, says you need at least ten cases per variable. That is
an absolute minimum: better results need more.
2. As you suspect, finite populations may help. The standard error of an
estimate (or the size of the sample needed for a given standard error) is
affected by the so called finite population correction which is (N-n)/(N-1)
where N=population and n=sample size. This you should look up in a
statistics text for more details.
3. A regression with a given sample size may be statistically significant if
all cases lie near the regression line, or not if cases are more scattered
around. If your data closely conform to a linear equation you may need a
Hope this helps.
De: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] En nombre de Rita
Enviado el: Wednesday, April 19, 2006 7:25 AM
Asunto: Minimum number of cases for computing correlation
I have a simple (?) statistics question.
When you run a correlation, which is the minimum number of case you have to
For regression maybe is 30 cases ? Under 30 cases regression is not
Is always referred to my population, i.e. 7 cases from a population of 50
units and 7 cases from a population of 1000 units are different ?
Thanks in advance