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The sample isn't 12 crashes. It is the 12 cars that crashed plus all the other cars that didn't.

by meric 13y ago

epi8 13y ago
That's... not true. The question is "how likely is there to be an electrical fire in the Tesla, given that it has crashed (or is crashing)" not "how likely is there to be an electrical fire". It's easy enough for things not to catch flame when they're being used properly; the real test is how things behave when other things are going wrong. That's not to say that this means all Tesla cars are fiery death-traps of doom. Just that the sample size really is the number of crashed cars.
- meric 13y ago
  Following your logic, we can ignore Tesla cars that catch fire without crashing, because we can assume they're not going to catch flame when they're used properly; We can assume cars that don't crash aren't going to catch fire anyway, so, even if they may happen, let's throw that data away, because we know our assumption holds true. That's ridiculous.
IgorPartola 13y ago
That is besides the point. We are talking about what happens when your Tesla S does crash. There is on "if" in the certainty that Teslas will be involved in accidents. The questions are "will they catch fire when they crash?" and also "how bad will that fire be for persons and property involved?"
- meric 13y ago
  There's also "Under what conditions when Tesla cars crash will they catch fire", and then you only look at your 12 crashes, and that's when everything goes wrong. The Space Shuttle Challenger exploded shortly after take-off in January 1986. Subsequent investigation determined that the cause was failure of the O-ring seals used to isolate the fuel supply from burning gases..... NASA staff had analysed the data on the relation between ambient temperature and number of O-ring failures (out of 6), but they had excluded observations where no O-rings failed, believing that they were uninformative. Unfortunately, those observations had occurred when the launch temperature was relatively warm (65-80 degF). http://www.datavis.ca/gallery/missed.php http://www.datavis.ca/gallery/missed.php Let's look at this question "how bad will that fire be for persons and property involved?" You look at your 12 crashes where fire occurs, so (e.g.) 6 crashes. Of 6 crashes 3 were accompanied with injuries. All 3 crashes that were accompanied by electrical fires and injuries occurred was when the car's speed was between (e.g.) 40mph and 50mph. Does that mean when the speed is not between 40mph and 50mph, people won't be injured when there's a crash and a fire? It means nothing like that but it's too easy to make a wrong conclusion; you're skipping all the other data where injuries and/or fires happen independently of crashes.
  - makomk 13y ago
    Sure, you can look at all the crashes, but you'll still run into exactly the same problems with insufficient sample size because now you're dealing with a rare event, which means the required sample size balloons massively.

The sample isn't 12 crashes. It is the 12 cars that crashed plus all the other cars that didn't.

by meric 13y ago

The sample isn't 12 crashes. It is the 12 cars that crashed plus all the other cars that didn't.

epi8 13y ago

That's... not true. The question is "how likely is there to be an electrical fire in the Tesla, given that it has crashed (or is crashing)" not "how likely is there to be an electrical fire". It's easy enough for things not to catch flame when they're being used properly; the real test is how things behave when other things are going wrong. That's not to say that this means all Tesla cars are fiery death-traps of doom. Just that the sample size really is the number of crashed cars.

meric 13y ago
Following your logic, we can ignore Tesla cars that catch fire without crashing, because we can assume they're not going to catch flame when they're used properly; We can assume cars that don't crash aren't going to catch fire anyway, so, even if they may happen, let's throw that data away, because we know our assumption holds true. That's ridiculous.

IgorPartola 13y ago

That is besides the point. We are talking about what happens when your Tesla S does crash. There is on "if" in the certainty that Teslas will be involved in accidents. The questions are "will they catch fire when they crash?" and also "how bad will that fire be for persons and property involved?"

meric 13y ago
There's also "Under what conditions when Tesla cars crash will they catch fire", and then you only look at your 12 crashes, and that's when everything goes wrong. The Space Shuttle Challenger exploded shortly after take-off in January 1986. Subsequent investigation determined that the cause was failure of the O-ring seals used to isolate the fuel supply from burning gases..... NASA staff had analysed the data on the relation between ambient temperature and number of O-ring failures (out of 6), but they had excluded observations where no O-rings failed, believing that they were uninformative. Unfortunately, those observations had occurred when the launch temperature was relatively warm (65-80 degF). http://www.datavis.ca/gallery/missed.php http://www.datavis.ca/gallery/missed.php Let's look at this question "how bad will that fire be for persons and property involved?" You look at your 12 crashes where fire occurs, so (e.g.) 6 crashes. Of 6 crashes 3 were accompanied with injuries. All 3 crashes that were accompanied by electrical fires and injuries occurred was when the car's speed was between (e.g.) 40mph and 50mph. Does that mean when the speed is not between 40mph and 50mph, people won't be injured when there's a crash and a fire? It means nothing like that but it's too easy to make a wrong conclusion; you're skipping all the other data where injuries and/or fires happen independently of crashes.
- makomk 13y ago
  Sure, you can look at all the crashes, but you'll still run into exactly the same problems with insufficient sample size because now you're dealing with a rare event, which means the required sample size balloons massively.