Comparison of ‘Power For Comparing Two Means’ to other public software programs and statistical textbook.

Date last tested: 7/11/05.

| CI %, | Mean difference (Group1 – Group2), n1, s1, n2, s2,
Data input | 95%, 5, 100, 15.34, 100, 18.23 | 95%, -0.24, 50, 0.64, 50, 0.76 | 95%, 5, 100, 18.23, 100, 15.34 | 95%, 5, 30, 18.23, 30, 15.34 | 95%, -4, 30, 18.23, 30, 15.34
OpenEpi | 55.52% | 40.06% | 55.52% | 20.89% | 14.89%
Rosner | 55.5% | 40.1% | NA | NA | NA
PEPI | 55.1% | ? | 55.1% | 20.35% | ?
UCLA Department Of Statistics | 55.1% | 39.4% | 55.1% | 20.3% | 14.5%

‘CI’ Confidence interval; ‘n1’ sample size of Group 1; ‘s1’ standard deviation of Group 1 mean; ‘n2’ sample size of Group 2; ‘s2’ standard deviation of Group 2 mean;

? Wrong result due to negative mean difference

Reference:

· Bernard Rosner. Fundamentals of Biostatistics (5th edition).

· PEPI: Abramson JH and Gahlinger PM (2001). Computer program for epidemiologists: PEPI version 4.0. Sagebrush Press, Salt Lake City. Used POWR.EXE version 4.0.

· UCLA Department Of Statistics. (http://calculators.stat.ucla.edu/powercalc/normal/n-2-unequal/n-2-uneq-var-power.php)