For Exercises 20 and 21, test whether the population medians differ, using level of significance . The data represent independent random samples.
20.
| Sample 1 | 11 | 14 | 17 | 13 | 18 | 12 | 10 | ||
| Sample 2 | 17 | 15 | 15 | 15 | 18 | 18 | |||
| Sample 3 | 11 | 19 | 18 | 12 | 11 | 12 | 11 | 15 | |
| Sample 4 | 21 | 22 | 20 | 21 | 23 | 19 | 17 | 23 | 24 |