Statistics › Section H · Confidence intervals › Topic H.3
Interval for a mean with the t distribution
The previous topic's formula needed one thing real studies rarely have: a known population spread. When the sample's s must stand in for σ, the interval grows slightly wider and the normal's z* gives way to the t distribution's critical values - honesty, priced in degrees of freedom.
In this topic
- The realistic case: σ unknown
- The t distribution and its story
- The one-sample t interval
- Conditions for t procedures
- Worked example: lightbulb lifetimes
- Worked example: the price of estimating σ
- Confidence interval or prediction interval?
- Robustness and alternatives
- Common mistakes to avoid
- Key takeaways
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