A study looked at number of cavity children per 100 in 18 NorthAmerican cites before and after public water fluoridation projects.The following table lists the data.
City | Before | After |
1 | 49.2 | 18.2 |
2 | 30 | 21.9 |
3 | 16 | 5.2 |
4 | 47.8 | 20.4 |
5 | 3.4 | 2.8 |
6 | 16.8 | 21 |
7 | 10.7 | 11.3 |
8 | 5.7 | 6.1 |
9 | 23 | 25 |
10 | 17 | 13 |
11 | 79 | 76 |
12 | 66 | 59 |
13 | 46.8 | 25.6 |
14 | 84.9 | 50.4 |
15 | 65.2 | 41.2 |
16 | 52 | 21 |
17 | 50 | 32 |
18 | 12 | 20 |
a. Please test whether there is a significant change in numberof cavity children per 100 after and before public waterfluoridation. Make sure you include all the five steps in thehypothesis testing questions.
b. What is the 95% confidence interval for the change?
