Day 21: Statistics for Business Applications

Last Time: CI for a proportion p
- Confidence interval estimator of p (when p is unknown!)
  - We can try to use p hat (the estimate of p)
  - Conservative standard error: use p=.5
  - Nielson example (recode, using Manip->code->numeric to numeric: 1 -> 1, 2:5 -> 0)
- Sample size calculations for p
Return problems 12.1-12.2
Questions about CI and proportions?
Homework for section 12.4 due next time
Today: Difference between two means
- Today, we'll worry only about the case of equal variances.
- Heights of NKU students: males versus females.
- Example handout (assuming equal variances)
Next time: Finish sections 13.1-2 - inference about the difference of two means

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