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FrameBenignly comments on Wear a Helmet While Driving a Car - Less Wrong Discussion

47 Post author: James_Miller 30 July 2015 04:36PM

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Comment author: FrameBenignly 01 August 2015 06:15:07PM *  4 points [-]

From the CDC:

Most drivers and passengers killed in crashes are unrestrained. 53% of drivers and passengers killed in car crashes in 2009 were not wearing restraints.

Seat belts dramatically reduce risk of death and serious injury. Among drivers and front-seat passengers, seat belts reduce the risk of death by 45%, and cut the risk of serious injury by 50%.

Seat belts prevent drivers and passengers from being ejected during a crash. People not wearing a seat belt are 30 times more likely to be ejected from a vehicle during a crash. More than 3 out of 4 people who are ejected during a fatal crash die from their injuries.

I bet a lot of TBI is due to being ejected from the vehicle.

Comment author: Houshalter 02 August 2015 02:48:20AM 2 points [-]

But what about the 47% who die who are wearing seat belts? Is that number even different than the base rate of people who wear seat belts?

Comment author: FrameBenignly 02 August 2015 03:02:53PM 0 points [-]

Well, to use the numbers given, if P(death) when you don't wear a seatbelt equals 1 and P(death) when you do equals 0.55, and 53 people die not wearing a seatbelt and 47 die wearing one, then 1 x A1 = 53 and 0.55 x A2 = 47. A1=53 and A2=85.45. A2/(A1+A2) = 0.617. So 62% of people are wearing a seatbelt at any given time.

I'm assuming they're calcing the two figures given the same methods which is not a given. They might be using real world figures for the former statistics and car crash simulator numbers for the latter statistics which would make more sense but throw my calculation off. 62% seems low to me.

Comment author: Houshalter 03 August 2015 06:12:58AM 0 points [-]

I am certain that the P(death|~seat belt) != 1.

Comment author: FrameBenignly 03 August 2015 06:43:05AM 1 point [-]

That's irrelevant. As long as the ratio of seatbelt to not seatbelt is 55/100, you'll end up with the same answer. ~seatbelt could be 0.1 or 0.03 or 0.00007.

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