he number of sub-groups (or “comparison” groups) is another consideration in the determination of a sufficient sample size. Since the parameter must be measured for each sub-group, the size of the sample for each sub-group must be sufficiently large to permit a reasonable (sufficiently narrow) estimation.
Treat each sub-group as a population and then use the table to determine the recommended sample size for each sub-group. Then use a stratified random sampling technique within each sub-group to select the specific individuals to be included.
If you would like to calculate sample sizes for different population sizes, confidence levels, or margins of error, download the Sample Size spreadsheet and change the input values to those desired.
Download the spreadsheet by clicking on the download button:
Note: The spreadsheet was designed for a 17” monitor, so you may have to resize it (“Zoom” it out).