In the accepted hierarchy of evidence generation, the results of a randomized, controlled clinical trial usually take precedence over other forms of evidence such as meta-analysis and observational studies.
In healthcare, our gold standard for good evidence is the randomizedcontrolledtrial, in which, for example, half the patients receive a new drug and half receive a placebo.
The authors noted that there has never been a controlled clinical trial of parachutes, and facetiously suggested that one be conducted in which subjects were randomized to jump from a plane either with or without a device.