4. 15-1 Introduction
Most of the hypothesis-testing and confidence interval procedures discussed in previous chapters are based on the assumption that we are working with random samples from normal populations.
These procedures are often called parametric methods
In this chapter, nonparametric and distribution free methods will be discussed.
We usually make no assumptions about the distribution of the underlying population.

5. 15-2 Sign Test 15-2.1 Description of the Test
The sign test is used to test hypotheses about the median of a continuous distribution.
Let R+ represent the number of differences
that are positive.

6. 15-2 Sign Test 15-2.1 Description of the Test
If the following hypotheses are being tested:
The appropriate P-value is

7. 15-2 Sign Test 15-2.1 Description of the Test
If the following hypotheses are being tested:
The appropriate P-value is

8. 15-2 Sign Test 15-2.1 Description of the Test
If the following hypotheses are being tested:
If r+ < n/2, then the appropriate P-value is
If r+ > n/2, then the appropriate P-value is

9. 15-2 Sign Test
Example 15-1

10. Example 15-1

11. 15-2 Sign Test
Example 15-1

12. 15-2 Sign Test
The Normal Approximation

13. 15-2 Sign Test
Example 15-2

14. 15-2 Sign Test
Example 15-2

15. 15-2 Sign Test
Sign Test for Paired Samples

16. 15-2 Sign Test
Example 15-3

17. 15-2 Sign Test
Example 15-3

18. 15-2 Sign Test
Example 15-3

19. 15-2 Sign Test 15-2.3 Type II Error for the Sign Test
Figure 15-1 Calculation of  for the sign test. (a) Normal distributions. (b) Exponential distributions

20. 15-3 Wilcoxon Signed-Rank Test
The Wilcoxon signed-rank test applies to the case of symmetric continuous distributions.
Under this assumption, the mean equals the median.
The null hypothesis is H0:  = 0

21. 15-3 Wilcoxon Signed-Rank Test
Example 15-4

22. Example 15-4

23. 15-3 Wilcoxon Signed-Rank Test
Example 15-4

24. 15-3 Wilcoxon Signed-Rank Test
Large-Sample Approximation

25. 15-3 Wilcoxon Signed-Rank Test
Paired Observations
Example 15-5

26. 15-3 Wilcoxon Signed-Rank Test
Paired Observations
Example 15-5

27. 15-3 Wilcoxon Signed-Rank Test
Paired Observations
Example 15-5

28. 15-4 Wilcoxon Rank-Sum Test
Description of the Test
We wish to test the hypotheses

29. 15-4 Wilcoxon Rank-Sum Test
Description of the Test
Test procedure:
Arrange all n1 + n2 observations in ascending order of magnitude and assign ranks.
Let W1 be the sum of the ranks in the smaller sample.
Let W2 be the sum of the ranks in the other sample. Then:
W2 = [(n1 + n2)(n1 + n2 + 1)]/2 – W1

30. 15-4 Wilcoxon Rank-Sum Test
Example 15-6

31. 15-4 Wilcoxon Rank-Sum Test
Example 15-6

32. Example 15-6

33. 15-4 Wilcoxon Rank-Sum Test
Example 15-6

34. 15-5 Nonparametric Methods in the Analysis of Variance
The single-factor analysis of variance model for comparing a population means is
The hypothesis of interest is

35. 15-5 Nonparametric Methods in the Analysis of Variance
The test statistic is
Computational method

36. 15-5 Nonparametric Methods in the Analysis of Variance
Example 15-7

37. Example 15-7