Robert,
There is no general rule about the ratio of cases to variables. Only
yesterday, there was an informative discussion of how the desired minimum
ratio of cases to variables in multiple regression depends greatly on such
issues as statistical power and effect sizes. I am not sure what analysis
you are proposing to do, but may I suggest that you look into the topic of
statistical power analysis.
HTH,
Stephen Brand
For personalized and professional consultation in statistics and research
design, visit
www.statisticsdoc.com
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]]On Behalf Of
Robert Marshall
Sent: Thursday, March 08, 2007 11:41 AM
To:
[hidden email]
Subject: Number of Variables and Sample Size Question
Hi list,
At one time I read/heard that for every variable, approximately 20 subjects
are needed, as a general rule of thumb. Does that hold true generally, and
does anyone know of a good reference for a general (or specific) rule.
Much thanks,
Robert
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