Statistics › Section H · Confidence intervals › Topic H.5
Choosing the sample size
Every interval so far was computed after the data arrived. Sample-size planning runs the arithmetic the other way: state the margin you need, pick a level, and solve for n - the most practical question in the chapter, because it decides the budget.
In this topic
- Design before data
- The logic: invert the margin
- Sample size for a proportion
- Worked example: the national poll
- Worked example: the coffee study's size
- The quadratic price of precision
- Round up, always
- Choosing the inputs honestly
- Common mistakes to avoid
- Key takeaways
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