Calculating power and sample size for study design

Note: The web calculator pages include links to JavaScript-based forms for easy calculation of power and sample size for study planning.

For an extensive list of alternative and more comprehensive sources of help, see for example: UCSF Biostatistics - Power and Sample Size Programs.

Using the web calculator, the following is possible:

• Calculation of the power and sample size for proportions (relative frequencies) of two independent samples
• Calculation of the confidence interval for the difference of two proportions
• Comparison of the mean value with a reference value (t-test for one sample)
• Comparison of means between two independent samples (t-test for two samples)
• Comparison of a proportion (rel. frequency) to a reference value
• Comparison of proportions (rel. frequencies) between two independent samples
• Unmatched case-control studies