The New Mexico State Highway Department is charged with maintaining all state roads in good condition. One measure of condition is the number of cracks present in each 100 feet of roadway. From the department’s yearly sample, the following data were obtained:
| 4 | 7 | 8 | 9 | 9 | 10 | 11 | 12 | 12 | 13 |
| 13 | 13 | 13 | 14 | 14 | 14 | 15 | 15 | 16 | 16 |
| 16 | 16 | 16 | 17 | 17 | 17 | 18 | 18 | 19 | 19 |
Calculate the interfractile ranges between the 20th, 40th, 60th, and 80th percentiles.
Solution
The data are in table
