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scott wrote:
>> For example, just the other day I was on the London Underground, and I
>> wondered: How the **** do they get the trains onto the track?
>> Something like the Circle line is completely subterranian, and I'm
>> pretty sure the factory where they make the carrages isn't. And it's
>> not like you can just take a train carrage down the escalator with you...
>
> The Circle line will have connections to other tracks that come up above
> ground. There are lots of connections that are not marked on the public
> underground map. They are needed for things like train repairs and
> replacements, and if some lines have fewer trains during busy periods,
> they need somewhere to park the other trains!
Yeah, I guess so...
>> This analysis works only if events are statistically *independent*, of
>> course. In the case of a flood, they might not be.
>
> Yep, floods are influenced by things like sun-spots, which follow patterns.
I was thinking more along the lines that a flood might well change the
characteristics of the flooded land / water courses through it, and
these changes may well affect the probability of another flood happening
(although I couldn't say in which direction).
>> In the second analysis, if a dice is rolled and almost never turns up
>> a 6, this could be taken as evidence that the dice is biased, in which
>> case the probability is not actually 1/6.
>
> Also the probability of a flood likely changes dramatically over time,
> before you get a chance to calculate a good estimate of the probability.
Probability is of course relative too.
The probability that the next letter in a sentence is a U is about 2.7%.
However, the probability that the next letter is a U *given that* the
previous letter was Q is more like 90%.
You might argue that that's because these events aren't independent. But
consider that the chance of rolling two 6's is 1/6^2, but the chance of
rolling two 6's *given that* you've already rolled one is 1/6 (i.e., 6
times more probable).
Probability: It depends on what you calculate.
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