1. Chapter 10 Statistical Inference for Two Samples Twice as much fun as one sample

3. 10-2 Inference for a Difference in Means of Two Normal Distributions, Variances Known Two populations – count them, 1,..2

4. More on Two Normals Assumptions

5. Oh yes, the test statistic

6. Example 10-1

9. 10-2.2 Type II Error and Choice of Sample Size Two-sided alternative: One-sided alternative: Now go to the Operating Characteristic Curves (VIIa-d)

10. Sample Size Formulas

11. Example 10-3

12. 10-2.3 Confidence Interval on a Difference in Means, Variances Known

13. CI Example 10-4

14. Other Useful Formulae Upper Confidence Bound Lower Confidence Bound Choice of Sample Size

15. 10-3.1 Hypotheses Tests for a Difference in Means, Variances Unknown Case 1:

16. The Two-Sample or Pooled t-Test

17. Example 10-5 We must do a difference of means test on this data.

18. Example 10-5

20. Minitab Output for Example 10-5

21. 10-3.2 Type II Error and Choice of Sample Size

22. Chart VII(e) d =.74  =.15 d =.74  =.15

23. 10-3.1 Hypotheses Tests for a Difference in Means, Variances Unknown Case 2: is distributed approximately as t with degrees of freedom given by

24. Example 10-6

25. The Data in a Normal Prob Plot

26. Example 10-6 (steps 1-5)

27. Example 10-6 (steps 6- 8)

28. Mean of Two Normal Distributions – Variance Unknown – Confidence Intervals Case 1:

29. Mean of Two Normal Distributions – Variance Unknown – Confidence Intervals Case 2:

30. The Next Example Louie Lush has collected the following data concerning the number of ounces of beer consumed per week by the typical UD student and the typical Wright-State student. Assuming the population variances are equal construct a 90% confidence interval for the difference in mean beer consumption between the two schools. Data: Ounces per student per week Wright State Univ of Dayton Sample mean60.465.3 Sample Variance31.444.82 Sample size1012 Pooled Variance:

31. More Next Example Wright State Univ of Dayton Sample mean60.465.3 Sample Variance31.444.82 Sample size1012 Unequal Variances: If you are interested in establishing a tavern near one of the two campus which one would you choose?

32. On to Excel…then Minitab These 2-sample tests are great but what can Excel do for me? To the Ever Excellent Excel Examples

33. Happiness is working a stat problem. Next Class I always work all the problems in the book.