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)