Beating sunburn with broccoli. Some recent studies suggest that compounds in broccoli may be helpful in combating the effects of overexposure to ultraviolet radiation. Based on these studies we hope to show that a cream consisting of a broccoli extract reduces sunburn pain. Sixty patients suffering from severe sunburn and needing pain relief are available. We will apply the cream to the sunburn of each patient and ask them an hour later, "About what percent of pain relief did you experience?"

(a) Why should we not simply apply the cream to all 60 patients and record the responses?

(b) Outline the design of an experiment to compare the cream's effectiveness with that of an over-the-counter product for sunburn relief and of a placebo.

(c) Should patients be told which remedy they are receiving? How might this knowledge affect their reactions?

(d) If patients are not told which treatment they are receiving, the experiment is single-blind. Should this experiment be double-blind also? Explain.