A study is to be made of the relative effectiveness of two kinds of cough medicines in increasing sleep. Six people with colds are given medicine A the first night and medicine B the second night. Their hours of sleep each night are recorded. The data are: The sleeping hours for people who took medicine A are 4.8, 4.1, 5.8, 4.9, 5.3, and 7.4. The sleeping hours for the same people who took medicine B are 3.9, 4.2, 5, 4.9, 5.4, and 7.1. To test whether the data indicate a significant difference in effectiveness of the two medicines, the appropriate test to use is:
a. Paired t-test
b. None
c. Two independent samples t-test
d. One sample z-test