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The 384 survey sample size

Stat card: 384 survey responses give a 5% margin of error at 95% confidence for any large population, with the number barely moving above about 20,000 people.
The number comes from the standard sample size formula with p set to 0.5.
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384 is the standard survey sample size for a 95% confidence level and a 5% margin of error when the population is large. It comes from the formula n = z squared times p times one minus p, divided by e squared, with z at 1.96, p at 0.5 and e at 0.05. Above about 20,000 people, the population size stops changing the answer.

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384 responses give a 5% margin of error at 95% confidenceFor any large population. The number barely moves above about 20,000 people.

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Related

Table of the survey sample size needed at 95% confidence and a 5% margin of error for populations from 100 to 100,000 or more, topping out at 384.

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