Does the release of a Harry Potter book lead children to spend more time reading and thus reduce the number of accidents they have? Doctors in England compared the number of emergency room visits due to musculoskeletal injuries to children aged 7 to 15 during two types of weekends: (1) following the release dates of two books in the Harry Potter series and (2) during 24 "control" weekends, for one hospital.The following table shows the data, with the "Harry Potter weekends" in italics.
| WEEKEND |
INJRIES |
WEEKEND |
INJURIES |
| 6/7/2003 |
63 |
7/10/2004 |
57 |
| 6/14/2003 |
77 |
7/17/2004 |
66 |
| 6/21/2003 |
36* |
7/24/2004 |
62 |
| 6/28/2003 |
63 |
6/4/2005 |
51 |
| 7/5/2003 |
75 |
6/11/2005 |
83 |
| 7/12/2003 |
71 |
6/18/2005 |
60 |
| 7/19/2003 |
60 |
6/25/2005 |
66 |
| 7/26/2003 |
52 |
7/2/2005 |
74 |
| 6/5/2004 |
78 |
7/9/2005 |
75 |
| 6/12/2004 |
84 |
7/16/2005 |
37* |
| 6/19/2004 |
70 |
7/23/2005 |
46 |
| 6/26/2004 |
75 |
7/30/2005 |
68 |
| 7/3/2004 |
81 |
8/6/2005 |
60 |
(a) Given the nature of the data, can we make an inference about the release of Harry Potter books causing a change in accidents? Why or why not?
(b) The average for the Harry Potter weekends is 36.5, with a standard deviation of 0.7. The corresponding numbers for the other (control) weekends are 67.4 and 10.4. Use a t test to investigate the claim that the small number of injuries during Harry Potter weekends is consistent with chance variation. Use α = 0.01.