The Calculators and Utilities provided below may help you in developing your study.

Sample Size -- Means

Instructions: Enter parameters in the Red cells. Answer will appear in the blue cells.

  • Q1 = proportion of subjects in group 1
  • E = Effect Size
  • S = Standard Deviation in the population
Alpha (Two-tailed)BetaQ1Q2ESE/S

A = 0.00
B = 0.00
C = 0.00
AB/C = 0.00

Because the formula used here is based on approximating the t statistic with a z statistic, it will slightly underestimate the sample size when N is less than about 30.

Software utilities by Michael Kohn ( and Mike Jarrett (

Disclaimer: Software is provided on an as-is basis and no warranty is made of any kind. Calculations are believed accurate but should be verified by the user