In spite of what may seem obvious, medical research has shown that being cold isn't related to catching a cold. Suppose that in one such study, 40 subjects were exposed to cold viruses. Then half of the subjects were randomly assigned to remain in a cold room for several hours, and the other half remain in a room kept at ordinary room temperature. At the end of the experiment, the numbers of subjects who catch a cold are as shown in the following table:
|
cold room
|
normal temperature room
|
Total
|
|
caught cold
|
14
|
12
|
26 |
|
no cold
|
6
|
8
|
14
|
|
Total
|
20
|
20
|
40
|
a. What is the null hypothesis?