Table MGT1U. Single one-way between means contrast (unequal n’s)

Power, sample size, or effect size are computed using central and non-central F. For MGT1U, the numerator and denominator degrees of freedom are 1 and (N-G), and the non-centrality parameter is the number of cases in group 1 times the square of the effect size. The effect size is defined in the row title in the table. See O’Brien, R.G., Muller, K.E. (1993) “Unified Power Analysis for t-tests through Multivariate Hypotheses”, in Edwards, L.K. (Ed.), Applied Analysis of Variance in Behavioral Science, Marcel Dekker, New York. Pages 297-344. See nQuery Advisor® manual Appendix for details of computing methods for F and non-central F. Figure MGT1U shows computations for an example contrast labeled “Dom vs {Ord & Loners}” taken from O’Brien, R.G. (1998) UnifyPow: A SAS Module/Macro for Sample Size Analysis, see http://www.bio.ri.ccf.org/power.html; all additional examples from this pdf also tested in nQuery Advisor®.

Figure MGT1U. In the first column, nQuery Advisor® 7.0 solved for power, in the second column for sample size and in the third column for effect size.