Two researchers are both interested in determining whether large doses of vitamin C can help prevent the common cold. Each obtains a sample of n = 20 college students.
a. The first researcher interviews each student to determine whether they routinely take a vitamin C supplement. The researcher then records the number of colds each individual gets during the winter. Is this an experimental or a nonexperimental study? Explain your answer.
b. The second researcher separates the students into two roughly equivalent groups. The students in one group are given a daily multivitamin containing a large amount of vitamin C, and the other group gets a multivitamin with no vitamin C. The researcher then records the number of colds each individual gets during the winter. Is this an experimental or a nonexperimental study? Explain your answer.