9. A researcher recruits 20 sets of identical twins from an online group for twins. He randomly
selects one twin from each set to spend a year in space, and the other one stays on Earth. After
the year, he has all of the twin undergo a thorough physical exam. He's interested in seeing
whether there are differences in the physiologies of the twins who stayed on Earth and the twins
who went to space. Which of the following best describes the data and test the researcher
would use to examine this question?
a. Observational, paired t-test
b. Observational, independent samples t-test
c. Experimental, paired t-test
d. Experimental, independent samples t-test
e. None of the above