How many subjects to screen? A practical procedure for estimating multivariate normal probabilities for correlated variables. |
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Authors: | McGraw, Kenneth O. Gordji, Sohrab Wong, S. P. |
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Abstract: | Suggests a practical procedure for estimating the number of Ss that need to be screened to obtain a sample of fixed size that meets multiple correlated criteria. The procedure is based on the fact that least squares regression provides a good quadratic fit for Monte Carlo estimates of multivariate probabilities when they are plotted as a function of mean pairwise correlations (r) for the criterion variables. The equations given here can be used to predict selected 3- to 5-variable joint probabilities with reasonable accuracy as long as pairwise correlations for the selection criteria range from .10 to .90. (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
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