Statistics › Section H · Confidence intervals › Topic H.2
Interval for a mean with known sigma
A point estimate names one number; an interval tells how far that number deserves to be trusted. This topic builds the confidence interval for a mean in the rare, clean case where the population's spread is known in advance - the prototype for every interval that follows.
In this topic
- From point to interval
- The formula and its margin
- Confidence levels and critical values
- What "confident" means
- Worked example: coffee deliveries
- Worked example: one data set, three levels
- Design leverage: the sample size
- The known-sigma caveat
- Common mistakes to avoid
- Key takeaways
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