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Dear all, I know there are some questions and disagreements on different ways of sample size calculation for a regression model. If I take the example of a linear model with k number of independent variables; some say 3*k=n is the minimum necessary for a good power, and some say k*k*k is enough. The difference is huge and the researches approach the question very differently. Many published data even do not speak about sample size calculation. I've got two questions and your responses are very appreciated: 1) are you aware of any published material on the issue of sample size calculation for regression models? the most that I've seen don't go further than a linear model with 1 independent variable. 2) Another possibility is to break down the question to a single coefficient (Bi) - the coefficient which is the most important one for the research objectives- and do a real calculation on that. Do you know any reference for it or a practical example? Yours Arash -- Arash Rashidian, MD Health Services Research Scholar Department of Health Sciences and Clinical Evaluation Alcuin College, University of York York, YO10 5DD, UK Tel: +44 (0)1904 434498 Mob: +44 (0)7870466148 Fax: +44 (0)1904 434517 email: [log in to unmask] http://www-users.york.ac.uk/~ar130/