这篇幽默的文章讲述了一位庞蒂亚克车主遇到的奇怪问题：每次买香草冰淇淋后，他的车就无法启动，但买其他口味的冰淇淋则一切正常。通用汽车公司的庞蒂亚克部门收到投诉后，派工程师调查，发现问题并非冰淇淋本身，而是购买香草冰淇淋所需的时间较短。由于香草冰淇淋最受欢迎，被放在商店前面的独立柜台中以便快速取货，而其他口味则在商店后面，需要更长时间寻找和结账。较短的时间导致发动机没有足够的时间冷却，从而产生蒸汽锁现象，阻止汽车启动。这个故事告诉我们，即使看似疯狂的问题有时也是真实的，同时也提醒我们，数据只表明存在因果关系，而不一定是原因。

🍦一位庞蒂亚克车主发现了一个奇怪的现象：每次他购买香草冰淇淋后，他的车就无法启动，但购买其他口味的冰淇淋时，汽车启动正常。

👨‍🔧通用汽车公司的庞蒂亚克部门收到投诉后，派遣一位工程师进行调查。工程师经过多次实验，发现问题与购买冰淇淋的口味无关，而是与购买不同口味冰淇淋所需的时间有关。

⏱️原来，香草冰淇淋作为最受欢迎的口味，被单独放在商店前面的冰柜中，方便顾客快速取货。而其他口味的冰淇淋则放在商店后面，需要更长时间才能找到并结账。

🌡️购买香草冰淇淋所需的时间较短，导致发动机没有足够的时间冷却。发动机过热会导致蒸汽锁现象，从而阻止汽车启动。当购买其他口味的冰淇淋时，由于耗时较长，发动机有足够的时间冷却，因此汽车可以正常启动。

💡这个故事说明，即使看似荒谬的问题，背后也可能有其真实的、合理的解释。它也提醒我们，数据只能表明存在因果关系，并不能直接揭示原因。在解释现象时，我们需要考虑所有已知的知识和经验，寻找最合理的解释，而不是轻易接受看似神奇的结论。

Published on December 8, 2024 6:57 AM GMT

Story from https://www.cs.cmu.edu/~wkw/humour/carproblems.txt (my thoughts follow):

For those of us who understand that the obvious is not
always the solution, and that the facts, no matter how implausible,
are still the facts ...

A complaint was received by the Pontiac Division of General Motors:

"This is the second time I have written you, and I don't blame you
for not answering me, because I kind of sounded crazy, but it is a
fact that we have a tradition in our family of ice cream for dessert
after dinner each night. But the kind of ice cream varies so, every
night, after we've eaten, the whole family votes on which kind of ice
cream we should have and I drive down to the store to get it. It's
also a fact that I recently purchased a new Pontiac and since then my
trips to the store have created a problem. You see, every time I buy
vanilla ice cream, when I start back from the store my car won't
start. If I get any other kind of ice cream, the car starts just
fine. I want you to know I'm serious about this question, no matter
how silly it sounds: 'What is there about a Pontiac that makes it not
start when I get vanilla ice cream, and easy to start whenever I get
any other kind?'"

The Pontiac President was understandably skeptical about the letter,
but sent an engineer to check it out anyway. The latter was surprised
to be greeted by a successful, obviously well-educated man in a fine
neighborhood. He had arranged to meet the man just after dinner time,
so the two hopped into the car and drove to the ice cream store. It
was vanilla ice cream that night and, sure enough, after they came
back to the car, it wouldn't start.

The engineer returned for three more nights. The first night, the
man got chocolate. The car started. The second night, he got
strawberry. The car started. The third night he ordered vanilla.
The car failed to start.

Now the engineer, being a logical man, refused to believe that this
man's car was allergic to vanilla ice cream. He arranged, therefore,
to continue his visits for as long as it took to solve the
problem. And toward this end he began to take notes: he jotted down
all sorts of data, time of day, type of gas used, time to drive back
and forth, etc.

In a short time, he had a clue: the man took less time to buy
vanilla than any other flavor. Why? The answer was in the layout of
the store.

Vanilla, being the most popular flavor, was in a separate case at
the front of the store for quick pickup. All the other flavors were
kept in the back of the store at a different counter where it took
considerably longer to find the flavor and get checked out.

Now the question for the engineer was why the car wouldn't start
when it took less time. Once time became the problem -- not the
vanilla ice cream -- the engineer quickly came up with the answer:
vapor lock. It was happening every night, but the extra time taken to
get the other flavors allowed the engine to cool down sufficiently to
start. When the man got vanilla, the engine was still too hot for the
vapor lock to dissipate.

Moral of the story: even insane-looking problems are sometimes real.

There are times when people tell me that (metaphorically) their car won't start because of the vanilla ice cream spell.

I usually assign rather low probability to their claims that (metaphorically) "vanilla ice cream causes their car to not start".

But I also would still assign very low probability to the "vanilla ice cream spell" explanation of the causation even if I believed a lot of scientifically sound data was collected to support the causal link between "buying ice cream" and "car won't start".

I'm not "refusing the evidence" by not believing in the vanilla ice cream spell hypothesis. The data just says there's a causal link—it doesn't say why. Jumping to the spell hypothesis disregards everything else we know about physics—it's more likely that there's a more reasonable explanation we didn't think of. By reasonable, I mean an explanation that would add up to normality—that wouldn't require us to update our would model nearly as much.

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