An article in the San Luis Obispo Tribune (Sep- tember 7, 1999) described an experiment designed to investigate the effect of creatine supplements on the de- velopment of muscle ?bers. The article states that the researchers "looked at 19 men, all about 25 years of age and similar in weight, lean body mass, and capacity to lift weights. Ten were given creatine-25 grams a day for the ?rst week, followed by 5 grams a day for the rest of the study. The rest were given a fake preparation. No one was told what he was getting. All the men worked out under the guidance of the same trainer. The response variable measured was gain in fat-free mass (in percent)."

a. What extraneous variables are identi?ed in the given statement, and what strategy did the researchers use to deal with them?

b. Do you think it was important that the men participating in the experiment were not told whether they were receiving creatine or the placebo? Explain.

c. This experiment was not conducted in a double-blind manner. Do you think it would have been a good idea to make this a double-blind experiment? Explain.