Colds and vitamin C For some time there has been debate about whether regular large doses of vitamin C reduce the chance of getting a common cold.

a. Explain how you could design an experiment to test this. Describe all parts of the experiment, including

(i) what the treatments are, (ii) how you assign subjects to the treatments, and (iii) how you could make the study double-blind.

b. An observational study indicates that people who take vitamin C regularly get fewer colds, on the average.

Explain why these results could be misleading.