A novel alternative medical treatment for heart at- tacks seeds the damaged heart muscle with cells from the patient's thigh muscle ("Doctors Mend Damaged Hearts with Cells from Muscles," San Luis Obispo Tribune, November 18, 2002). Doctor Dib from the Arizona Heart Institute evaluated the approach on 16 patients with severe heart failure. The article states that "ordinarily, the heart pushes out more than half its blood with each beat. Dib's patients had such severe heart failure that their hearts pumped just 23 percent. After bypass surgery and cell injections, this improved to 36 percent, although it was impossible to say how much, if any, of the new strength resulted from the extra cells."
a. Explain why it is not reasonable to generalize to the population of all heart attack victims based on the data from these 16 patients.
b. Explain why it is not possible to say whether any of the observed improvement was due to the cell injections, based on the results of this study.
c. Describe a design for an experiment that would allow researchers to determine whether bypass surgery plus cell injections was more effective than bypass surgery alone.