Professor Fair believes extra time does not improve grades on exams. He randomly divided a group of 300 students into two groups and gave them all the same test. One group had exactly 1 hour in which to finish the test, and the other group could stay as long as desired. The results follow. Test at the .01 level of significance that time to do a test and test results are independent.
|
|
Exam |
Grades |
|
|
| Time |
A |
B |
C |
F |
Total |
| 1 hour |
23 |
42 |
65 |
12 |
142 |
| Unlimited |
17 |
48 |
85 |
8 |
158 |
| Column total |
40 |
90 |
150 |
20 |
300 |