Ken ([info]shadowplay2) wrote,
@ 2006-09-20 22:49:00
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can't escape technology
So yesterday morning I'm out on a field meeting, walking through seven foot tall cattails in the middle of a marsh on the way to take a look at endangered dragonfly habitat. There's a guy from U.S. Fish and Wildlife service behind me, and a guy from the landowner, a county agency, leading the way.

The county guys cell phone rings. Less than a minute after he takes that call, the federal guys cell phone rings. So I'm standing in the marsh watching this... and my cell phone rings. It's our mayor, 2,000 miles away, asking whether a particular day and time works for a meeting.

All three of us, in less than two minutes. What are the odds?

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[info]urockgyrl
2006-09-21 05:07 am UTC (link)
50/50 for the first guy
50/50 for the 2nd guy
and
50/50 for you

events have no "memory"

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(Deleted post)
Re: Joint probability
[info]urockgyrl
2006-09-21 08:10 pm UTC (link)
Sorry darlin... the events are independent... therefore independent probabilities all the way down...


Statistical independence

Two random events A and B are statistically independent if and only if

P(A * B) \ = \ P(A) P(B).

Thus, if A and B are independent, then their joint probability can be expressed as a simple product of their individual probabilities.

Equivalently, for two independent events A and B,

P(A|B) \ = \ P(A)

and

P(B|A) \ = \ P(B).

The meat is down here (also from WIKIPEDIA)
In other words, if A and B are independent, then the conditional probability of A, given B is simply the individual probability of A alone; likewise, the probability of B given A is simply the probability of B alone.

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Re: Joint probability
[info]urockgyrl
2006-09-21 08:45 pm UTC (link)
the phone calls were from different people to different people (3) who were standing together in a field

independent events

i think i read it correctly

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Re: Joint probability
[info]shadowplay2
2006-09-21 08:55 pm UTC (link)
Had to go and make me think about 20 year old stats classes, huh?

Yeah, calls from different people, none of whom knew about the other calls. Can't speak for the others, but my call was from someone who had no way of knowing where I was unless he had just talked to someone who did know. So independent events. But still, the odds of a call coming in at any particular moment of the day... for example, between 10:00 and 10:03 am CST... are going to be relatively small. No, I'm not going to calculate the probablility, would need to find my old books to do that, and I wasn't real crazy about those classes the first time :)

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