Researchers studied 393 patients in a hospital’s coronary care unit. In the experiment, volunteers were asked to pray daily for a patient’s rapid recovery and for the prevention of complications and death.

None of the patients knew if he or she was being prayed for. None of the volunteers or patients knew each other. The research team categorized how each patient fared as “good,” “intermediate,” or “bad.” They concluded that “prayed for” patients fared a little better than other patients—the experiment having documented results that seemed to support the prediction that prayer might have beneficial effects for seriously ill patients.

The results brought a storm of criticism, mostly from scientists who cited bias in the experimental design. For instance, the patients were categorized after the experiment was over, instead of as they were undergoing treatment, so the team already knew which ones had improved, stayed about the same, or gotten worse. Why do you suppose the experiment generated a heated response from many in the scientific community? Can you think of at least one other variable that might have affected the outcome of each patient’s illness?