StatTools : Sample Size for Differences in Measurements Between Unpaired Groups
Tables
Tables of Sample Sizes for Two Groups Tables of Sample Sizes for Multiple (>2) Groups References
These tables provides sample sizes (per group) needed to compare the means of 2 groups, assuming that the data is normally distributed, that the variance in the groups are similar, and that the sample sizes for the groups are the same
- Power = 1-β
- α = Probability of Type I Error
- es = Effect size = difference between means / population of within group Standard Deviation
Effect Size 0.05→1.00 Effect Size 1.05→2.00 Effect Size 2.05→3.00
Power0.80.90.95
Alpha0.10.050.010.0010.10.050.010.0010.10.050.010.001
es1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail1 tail2 tail
0.0536074947494762818031934512370136635256685268528407104151190515293167266852865986591039712618142531794019490
0.190212381238157120092338309534181315171417142103260529783825418417142166216626003156356544874875
0.15402551551699894104013771521585762762935115913251702186176296396311571404158619962168
0.2226310310394504586776857329429429527653746959104842954254265179089311241221
0.25145199199253323376498550211275275338418478614672275347347417507572720783
0.3101139139176225262346383147191191235291333428468191242242290352398501544
0.3575102102130166193255282108141141173214245315344141178178214259293369401
0.457787810012714819621783108108133165188242265108136136164199225283308
0.454562627910111815617266868610513014919221085108108130158178224244
0.537515164829612714053707086106121156170698888105128145182198
0.55314242536879105116445858718810112914158737387106120151164
0.626363645586789983749496074851091194861617489101127139
0.65223030394957768432424251637393102415252637786109119
0.71926263343506673283636445563818936454554667594103
0.75172323293844586424323239485571783140404858658390
0.8152020263339515721282834434963692835354251587379
0.85131818233034465019252531384356612531313746516571
0.9121616212731414517222227343950552228283441465863
0.95111515192428374115202025313545502025253037425357
1101414172226343714181822283241451823232733384852