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Researchers Show Parachutes Don't Work, But There's A Catch (npr.org)
Reader Beeftopia shares a report: Research published in a major medical journal concludes that a parachute is no more effective than an empty backpack at protecting you from harm if you have to jump from an aircraft. But before you leap to any rash conclusions, you had better hear the whole story. The gold standard for medical research is a study that randomly assigns volunteers to try an intervention or to go without one and be part of a control group. For some reason, nobody has ever done a randomized controlled trial of parachutes. In fact, medical researchers often use the parachute example when they argue they don't need to do a study because they're so sure they already know something works. Cardiologist Robert Yeh, an associate professor at Harvard Medical School and attending physician at Beth Israel Deaconess Medical Center, got a wicked idea one day. He and his colleagues would actually attempt the parachute study to make a few choice points about the potential pitfalls of research shortcuts.
They started by talking to their seatmates on airliners. [...] In all, 23 people agreed to be randomly given either a backpack or a parachute and then to jump from a biplane on Martha's Vineyard in Massachusetts or from a helicopter in Michigan. Relying on two locations and only two kinds of aircraft gave the researchers quite a skewed sample. But this sort of problem crops up frequently in studies, which was part of the point Yeh and his team were trying to make. Still, photos taken during the experiment show the volunteers were only too happy to take part. The drop in the study was about 2 feet total, because the biplane and helicopter were parked. Nobody suffered any injuries. Surprise, surprise. So it's technically true that parachutes offered no better protection for these jumpers than the backpacks.
They started by talking to their seatmates on airliners. [...] In all, 23 people agreed to be randomly given either a backpack or a parachute and then to jump from a biplane on Martha's Vineyard in Massachusetts or from a helicopter in Michigan. Relying on two locations and only two kinds of aircraft gave the researchers quite a skewed sample. But this sort of problem crops up frequently in studies, which was part of the point Yeh and his team were trying to make. Still, photos taken during the experiment show the volunteers were only too happy to take part. The drop in the study was about 2 feet total, because the biplane and helicopter were parked. Nobody suffered any injuries. Surprise, surprise. So it's technically true that parachutes offered no better protection for these jumpers than the backpacks.
Perhaps I would have been more accurate if I pointed out prognosis is an example of a variable readers might overlook. Obviously there can be many such factors, so any generalisation based on a specific study is fraught with peril.
On a related tangent, I've noticed this effect in the extreme for legal cases. Most Slashdot headlines about legal cases are wrong when they say a court decided an issue, as opposed to deciding a specific case. A court decides a result from the wording of a specific law, as applied to a specific party, given their conduct in a specific case.
For example, in consider a Masterpiece Bakeshop, the Colorado baker who wouldn't design a custom cake for a gay wedding. The Supreme Court ruled in his favor. The state of Colorado can't prosecute him for that case, the court ruled.
People think SCOTUS ruled that it's okay to discriminate against gay people. That's not what happened.
They did NOT rule that people can refuse to do business with gay people. They did not strike down the law. In fact, he's in court again now, for doing the same thing again. The facts of the case were:
The baker said he'd happily sell them anything on the shelf.
They wanted him to custom create an artwork celebrating their marriage, and he was unwilling to do that on religious grounds.
The state board said it's okay for artists, including bakers, to refuse to create messages they don't agree with - unless the artist is a Christian. The board chair said out loud, on the record in the hearing, that he was coming after the guy for being a &$@%* Christian.
The baker asserted that his First Amendment rights proclude the state from forcing him to make a statement celebrating gay marriage, including a statement in the form of a cake with certain decorations etc.
The court ruled that the state CAN force people to make statements celebrating gay marriage. What they can't do is explicitly target Christians for enforcement, openly going after people because they are Christian. The state has to at least uphold the appearance that they would enforce the law against an atheist who diagreed with gay marriage.
The point is, the generalisation people make from the case is entirely wrong.