Question: You are interested in determining whether an experimental birth control pull has the side effects of changing blood pressure. You randomly sample 10 women from the city in which you live. You give 5 of them a placebo for a month and then measure their diastolic blood pressure. Then you switch them to the birth control pill for a month and again measure their blood pressure. The other 5 women receive the same treatment except they are given the birth control pill first for a month, followed by the placebo for a month. The blood pressure readings are shown here. Note that to safeguard the women from unwanted pregnancy, another means of birth control that does not interact with the pill was used for the duration of the experiment.

Diastolic Blood Pressure

Subject No. Birth Control Pill Placebo

1 108 102

2 76 68

3 69 66

4 78 71

5 74 76

6 85 80

7 79 82

8 78 79

9 80 78

10 81 85

a. What is the alternative hypothesis? Assume a nondirectional hypothesis is appropriate.

b. What is the null hypothesis?

c. What is the value of t obtained.

d. What might we conclude using α = 0.05_{2 tail}?

e. What type error may have been made?

f. Calculate Cohen’s d.