This tool determines the sample size required to estimate a population proportion. You will need to provide the confidence level and desired margin of error. You can also provide a proportion estimate if known. If a proportion estimate is given, the sample size is computed using the following formula:
where zα/2 is the inverse cumulative probability
of the z distribution at 1 - &alpha/2,
is the proportion estimate,
, and E is the
margin of error.
If a proportion estimate is not given, the following formula is used:
To use this tool, provide the following inputs to the dialog: