Would you jump out of a plane if there were only 50/50 odds that your backpack contained a parachute? Probably not. Yet that is how a controlled study on the safety and efficiency of parachutes would work. You and several dozen others would be randomly sorted into two groups, handed either a parachute as part of the test group or an empty backpack as part of the control group, then asked to jump.
If such a study sounds absurd, it is probably good that one has never been conducted. Such a controlled, evidence-based test, that subjected half the participants to severe injury or death due to their placement in the control group, would be wildly unethical.
