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Put armor where there aren't bullet holes

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Re: Put armor where there aren't bullet holes

#51

Post by gjm11 »

werftgh wrote: post #33
silentbicycle wrote: post #27

Earlier quoted context omitted.

Do you have any citations for that? I'm not doubting you, but genuinely curious (and ambivalent about helmets). There seems to be a pervasive attitude in the US that if you're a cyclist hit by a car when you're not wearing a helmet, you're automatically at fault, because you're not being responsible. Which is weird, because the risk isn't coming from the bikes...and there's a good chance that it makes cycling seem mo…

Can't remember the name but an experiment by a prof from UCL showed that cars approached him more closely when he was wearing a helmet - but they gave him more space when he was wearing a long blonde wig. So the safest solution is a transvestite without a helmet.

Yeah, but wearing a transvestite is really uncomfortable.

Re: Put armor where there aren't bullet holes

#52

Post by Luc »

It's a nice story, but the distribution of the bullet holes in the illustration ( http://motherjones.com/files/images/blog_raf_bullet_holes.jp... ) looks a bit too neat to me. I wouldn't expect the bullet holes to be placed exactly so that a cursory glance makes it mind-blowingly obvious where the weak spots are, in a neatly symmetrical way. I'd expect a bit of frowning and thinking and calculating to be needed to figure that out.

So, for an article about 'obvious but wrong' conclusions, I think the illustration is kind of deceiving... unless I'm wrong!

Re: Put armor where there aren't bullet holes

#53

Post by jasonkester »

blasdel wrote: post #47
Vivtek wrote: post #37

Earlier quoted context omitted.

Reminds me of Neal Stephenson's character whose strategy for bike safety at night was to assume he was wearing reflective clothing and that everybody in a car would be paid a million dollars to kill him.

Another strategy is to actually wear OSHA-certified hyper-reflective clothing, such that the anyone would assume that a driver who hit him must have been paid a million dollars to do it. A friend of mine does this, he has a whole closet full of orange and silver sweatshirts that he wears every day . Last time he got hit by a car was years ago, but when the cops showed up they took one look at him and arrested the dri…

Would only work in the US.

Here in England, everybody wears that terrible neon reflective stuff every time they leave the house. Bicycle optional in many cases. They have no shame here.

The downside is that it makes me comparatively less easy to spot.

Re: Put armor where there aren't bullet holes

#54

Post by cperciva »

pg wrote: post #23
robg wrote: post #19

Earlier quoted context omitted.

I thought this too, but then realized the humans doing the shooting are also illogical. For instance, I could see how hitting the wings might feel effective and easy, but it's not a great strategy because the bullet holes don't really impact the flight capability.

WW II fighter pilots were very rational about what they aimed at. (I happen to have read a lot about this.)

How many WW2 fighter pilots were actually good enough shots that they could aim at part of a plane? I always figured that the difference between a good gunner and a bad gunner was whether they hit the plane at all.

Re: Put armor where there aren't bullet holes

#55

Post by bhickey »

silentbicycle wrote: post #28
BRadmin wrote: post #9

Survivorship bias: http://en.wikipedia.org/wiki/Survivorship_bias

Would you mind fleshing that out? Just posting two words and linking to wikipedia doesn't add much to the conversation, and people who care about maintaining the level of discourse on HN might heavily downvote you.

Suppose that we want to study the underlying genetics of a disease. To do this, we want to look at some people with the disease (cases) and some people without (controls). The trouble is that if the disease makes people more likely to die, they won't be enrolled in your study.

This is of particular concern for fast moving diseases like pancreatic cancer. In general this effect manifests as a bias against people with more severe disease -- occasionally these are exactly the people you want to study.

The simplest way to get around this is with an alternative study design. Rather than ascertaining cases and controls, you enroll a large number of individuals in a cohort. After that, you sit back and track the cohort for decades and watch for disease to emerge.

A famous example of this is the Religious Orders Study (http://www.rush.edu/rumc/page-1099611542043.html). A large number of Catholic brothers and sisters graciously agreed to participate on a study of Alzheimer's disease. The researchers recruited a cohort of non-demented clergy and have been tracking them for years. They perform annual cognitive tests on the participants to assess mental decline. All participants were gracious enough to consent to post-mortem brain donation. It would be impossible to get this sort of data with a case/control study.

Another type of ascertainment bias is population stratification which can generate all sorts of misleading results. Imagine that you're a scientist in Boston and you want to study sickle cell anemia. You phone up a doctor friend and say "Please send me the next 10 sickle cell cases and the next 10 non-sickle cell cases." After spending $300,000 and a year and a half on the project you find some great mutations. Ten minutes later you notice that all the markers you found are strongly associated with being African-American. Your cases included 9 persons of African ancestry and one of Mediterranean ancestry, while your controls matched the particular demographic blend that you'd expect to find around Boston. Oops.

I hope that helps.

p.s. Is anyone in London looking for smart people? E-mail me. ;)

Re: Put armor where there aren't bullet holes

#56

Post by VMG »

Luc wrote: post #52

It's a nice story, but the distribution of the bullet holes in the illustration ( http://motherjones.com/files/images/blog_raf_bullet_holes.jp... ) looks a bit too neat to me. I wouldn't expect the bullet holes to be placed exactly so that a cursory glance makes it mind-blowingly obvious where the weak spots are, in a neatly symmetrical way. I'd expect a bit of frowning and thinking and calculating to be needed to fi…

Maybe this is the sum of multiple planes illustrated on one

Re: Put armor where there aren't bullet holes

#57

Post by robg »

pg wrote: post #23
robg wrote: post #19

Earlier quoted context omitted.

I thought this too, but then realized the humans doing the shooting are also illogical. For instance, I could see how hitting the wings might feel effective and easy, but it's not a great strategy because the bullet holes don't really impact the flight capability.

WW II fighter pilots were very rational about what they aimed at. (I happen to have read a lot about this.)

I was thinking specifically about ground-to-air fire. Other flyers should know where to aim. Any evidence of this knowledge gap in the literature?

Re: Put armor where there aren't bullet holes

#58

Post by stcredzero »

blasdel wrote: post #47
Vivtek wrote: post #37

Earlier quoted context omitted.

Reminds me of Neal Stephenson's character whose strategy for bike safety at night was to assume he was wearing reflective clothing and that everybody in a car would be paid a million dollars to kill him.

Another strategy is to actually wear OSHA-certified hyper-reflective clothing, such that the anyone would assume that a driver who hit him must have been paid a million dollars to do it. A friend of mine does this, he has a whole closet full of orange and silver sweatshirts that he wears every day . Last time he got hit by a car was years ago, but when the cops showed up they took one look at him and arrested the dri…

Another strategy is to assume the drivers are wearing hyper-reflective clothing and that you've been paid a million dollars to hit them. Someone try that out and report back.

Re: Put armor where there aren't bullet holes

#59

Post by Vivtek »

donw wrote: post #50
quickpost wrote: post #38

Earlier quoted context omitted.

What Neal Stephenson book was that? Zodiac?

Yep, it's a description of Sangamon's method for dealing with the nightmare of Boston traffic.

I couldn't for the life of me remember the name of the book or the character - I do remember perfectly the gas-masked fish on the cover of the mass-market paperback, though.

Re: Put armor where there aren't bullet holes

#60

Post by kd0amg »

mattmaroon wrote: post #29

You must be careful when applying this sort of logic because it assumes that what happens to a plane after its shot is entirely deterministic, ie. if it gets shot in the tail fin it crashes, if it gets shot in the wing it doesn't. That may or may be accurate for planes (I really don't know) but may not for other things. Suppose anywhere the plane was shot led to a 1/5 chance of the plane crashing, meaning that all pl…

Suppose anywhere the plane was shot led to a 1/5 chance of the plane crashing, meaning that all places are equally deserving of armor. Suppose also that the wings comprised about 75% of the surface area of the plane. You'd see 3 planes returning with bullet holes in a wing for every 1 with a bullet hole somewhere else.

So do your study with the plane divided up into equal-sized sections. Or look for clustering and divide it based on that.

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