Which of the Following Is an Example of Paired Data

Multiple Choice

Which of the following is an example of paired data?

A) A random sample of students is asked how much money they made during the past summer. Results for males and females are compared.
B) A randomized experiment is done in which volunteers who want to lose weight are randomly assigned to either follow a specified diet or participate in an exercise program for 6 months. At the end of the study the two groups are compared to see which one had a higher proportion of people drop out of the study.
C) An observational study is conducted on a random sample of married couples to compare the average number of hours worked per week for the husband and the wife.
D) A random sample of students is asked on the first day of the quarter how many hours they slept the night before. The question is repeated for a new random sample of students on the first day of finals week.