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0 pointsfroobius6mo ago0 comments

You've added some useful context, but I think you're downplaying it's use. It's non-obvious, and in many cases better than just saying "we don't know". For example, if some company's server has been down for an hour, and you don't know anything more, it would be reasonable to say to your boss: "I'll look into it, but without knowing more about it, stastically we have a 50% chance of it being back up in an hour".

> The better thing to do is to get some even-specific knowledge, rather than trying to reason from a priori logic

True, and all the posts above have acknowledged this.

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tsimionescu6mo ago

> "I'll look into it, but without knowing more about it, stastically we have a 50% chance of it being back up in an hour"

This is exactly what I don't think is right. This particular outage has the same a priori chance of being back in 20 minutes, in one hour, in 30 hours, in two weeks, etc.

froobiusOP6mo ago

Ah, that's not correct... That explains why you think it's "trite", (which it isn't).

The distribution is uniform before you get the measurement of time taken already. But once you get that measurement, it's no longer uniform. There's a decaying curve whose shape is defined by the time taken so far. Such that the statement above is correct, and the estimate `time_left=time_so_far` is useful.

tsimionescu6mo ago

Can you suggest some mathematical reasoning that would apply?

If P(1 more minute | 1 minute so far) = x, then why would P(1 more minute | 2 minutes so far) < x?

Of course, P(it will last for 2 minutes total | 2 minutes elapsed) = 0, but that can only increase the probabilities of any subsequent duration, not decrease them.

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tsimionescu6mo ago

> "I'll look into it, but without knowing more about it, stastically we have a 50% chance of it being back up in an hour"

This is exactly what I don't think is right. This particular outage has the same a priori chance of being back in 20 minutes, in one hour, in 30 hours, in two weeks, etc.

froobiusOP6mo ago

Ah, that's not correct... That explains why you think it's "trite", (which it isn't).

tsimionescu6mo ago

Can you suggest some mathematical reasoning that would apply?

If P(1 more minute | 1 minute so far) = x, then why would P(1 more minute | 2 minutes so far) < x?

Of course, P(it will last for 2 minutes total | 2 minutes elapsed) = 0, but that can only increase the probabilities of any subsequent duration, not decrease them.

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j / k navigate · click thread line to collapse