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Old 15th Apr 2019, 15:27
  #138 (permalink)  
netstruggler
 
Join Date: Jan 2008
Location: LONDON
Posts: 26
Originally Posted by bnt View Post
Well, I was trying to answer the original question, which was about something that "proves conclusively". I just don't think that's possible to do with a controlled study, never mind a historical study (over time) or a longitudinal study (between different airports). So there are no guarantees, and we're left with "playing the odds".
?
Exactly the point that was made, tongue-in-cheek, in this report published online by the British Medical Journal. Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial

The study was forced to conclude that

Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention. However, the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps.
(As discussed on PPRuNe here )
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