On 15 Aug 2003 07:48:00 -0700, [EMAIL PROTECTED] wrote:
> I have a question concerning power and multiple regression. For my > study, I have 9 predictor variables, an alpha level of .05, and am > using .50 power. How would I estimate the number of participants for > my study? Thanks. How to estimate the N? I'd say: At least, read all the last chapters of Cohen's book on power analysis, and use his tables. Since you are asking the question, I am pretty sure that you need to read *at least* that much -- if you are to hope to understand the answer. He's going to encourage you to figure out if you really want nine predictors -- instead of one, or three. And do you really want to test them simultaneously? - do you hypothesize patterns? - or would you have more power (and much more intelligible tests) if you set up univariate tests and Bonferroni correction? -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html "Taxes are the price we pay for civilization." Justice Holmes. . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
