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\omega = Sqrt{ Sum_(1^no. groups ^) (observed proportion - expected proportion)}^2 ^} / expected proportion \omega = Sqrt{ Sum (1^no. groups ^) (observed proportion - expected proportion)^2 ^ / expected proportion

The spreadsheet gives the total sample size required for inputted group proportions (which should sum to 1), Type I error and a given power. The expected proportions are assume equal group sizes.

The expected effect size, $$\omega$$, defined below is from Cohen (1977,1988, Chap 7).

\omega = Sqrt{ Sum (1no. groups ) (observed proportion - expected proportion)2 / expected proportion

The thresholds 0.1, 0.3, 0.5 correspond to small, medium and large $$\omega$$ effect sizes.

None: FAQ/power/prop1sn (last edited 2014-09-04 11:57:34 by PeterWatson)