“presize”: precision based sample size calculation
Sample size calculations are an important part of clinical research. Too few participants and the study objectives cannot be fulfilled; too many participants can be a waste of resources. Basically, there are two methods to calculate the sample size:
- Sample size calculation based on hypothesis testing (traditionally used)
- Precision based sample size calculation
The 2nd method is more in line with the current movement towards confidence intervals and away from p-values (reference to Martin Bland (BMJ 339).
While most statistical software packages contain some sample size calculation algorithms, they are mostly for method 1 based on hypothesis testing.
R is a statistical computing program and language commonly used in research. Statisticians at the CTU Bern, on behalf of the SCTO Statistics and Methodology Platform, have developed the “presize” R-package to assist with precision based sample size calculations. It includes methods for descriptive statistics, absolute and relative differences, various measures of correlation, as well as diagnostic measures.
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