Statistics › Section H · Confidence intervals › Topic H.4
Interval for a proportion
More than half of the country approves, says the poll - and the honest question is how much wobble that number carries. The proportion confidence interval answers it, and every news-story margin of error is its half-width.
In this topic
- The pollster's interval
- The formula
- Conditions: counts must be large enough
- Worked example: the voter poll
- Worked example: clinic satisfaction
- What 95% confident means
- The margin covers only sampling error
- Confidence, width, and the population's size
- Common mistakes to avoid
- Key takeaways
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