5.23 Statistical significance. A randomized comparative experiment examines whether the usual care of patients with chronic heart failure plus aerobic exercise training improves health status compared with the usual care alone. The researchers conclude that usual care plus exercise training confers modest but statistically significant improvements in self-reported health status compared with usual care without training. Explain what “statistically significant” means in the context of this experiment, as if you were speaking to a patient who knows no statistics.
5.23 Even if aerobic exercise training had no impact on health status, there might be some difference in health status between the two groups. However, in this case the difference was so great that it is unlikely to have occurred by chance (if we assume that aerobic exercise is not effective). Therefore, we reject the assumption that aerobic exercise has no effect on health status.