How Do I Perform Power and Sample Size Calculations for a One Proportion Test?

1. Click SigmaXL > Statistical Tools > Power & Sample Size Calculators > 1 Proportion Test Calculator.
2. Select Solve For Power (1 – Beta). Enter Sample Size and Alternative Proportion as shown:
   
   
   
   Note that we are calculating the power or likelihood of detection given that the maximum difference between group means = 1, with sample size for each group = 30, 3 groups, standard deviation = 1, significance level = .05, and Ha: Not Equal To (two sided test).
   
   
3. Click OK. The resulting report is displayed:




A power value of 0.94 is acceptable, but note that the sample size n = 300, and the difference in proportion value is 0.1 or 10%! The sample size requirements for discrete data are much higher than those for continuous data.



4. To determine Power & Sample Size using a Worksheet, click SigmaXL > Statistical Tools > Power & Sample Size with Worksheet > 1 Proportion Test.
5. A graph showing the relationship between Power, Sample Size and Proportion Value can then be created using SigmaXL > Statistical Tools > Power & Sample Size Chart. See here for an example using the 1 Sample t-Test.