Sample Size and Confidence Interval Calculator
Use the
Sample Size calculator to determine the sample size you
will need for a given confidence interval (margin of
error). This is also useful for estimating the size of
the population needed to achieve a desired sample size.
Leave the "Population" field blank if the
population is more than 50,000.
Use the Confidence Interval calculator to determine the
confidence interval (margin of error) for a completed
study. This calculator is also useful for determining the
confidence interval for a specific question within a
completed study. For most calculations, the
“Percentage” can remain at “50”.
A 95% confidence level is sufficient for most market
studies. Most researchers prefer a confidence interval of
less than 4 percentage points. The lower the confidence
interval, the more reliable the study.
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