Sample Size Calculator
For an effectively large population, use z²p(1−p) divided by squared margin of error.
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How it works
For an effectively large population, use z²p(1−p) divided by squared margin of error.
Worked example
At 95% confidence, 5% margin, and p=50%, the estimate is 385 responses.
Keep in mind
Nonresponse and sampling design can require a larger sample.