5.18 Statistical signicance. 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 signicant improvements in self-reported health status compared with usual care without training. Explain what \"statistically signicant" means in the context of this experiment, as if you were speaking to a patient who knows no statistics