PDA

View Full Version : Probability of two things happening at the same time


Dr Chaos
Jul14-10, 04:49 AM
As there are an infinite number of time frames, does that mean that the probability of two things happening at the exact same time is one in infinity? (For example, two arrows hitting a target simultaneously).

If so, what is the probability of three things happening at the same time? Less than one in infinity?

mathman
Jul14-10, 03:31 PM
You are making things needlessly complicated. Both probabilities are 0.

Dr Chaos
Jul14-10, 08:00 PM
But surely it is possible for two arrows to hit a target at once?

CRGreathouse
Jul14-10, 08:27 PM
But surely it is possible for two arrows to hit a target at once?

http://en.wikipedia.org/wiki/Almost_surely

mathman
Jul15-10, 05:01 PM
Things that are possible may have zero probability. For example, everyone has a weight, but the probability that your weight is exactly a given value is zero. The point being if you are selecting from a continuous distribution, any given choice has a zero probability - you can only meaningfully talk about probability of a value in some interval.

Dr Chaos
Jul15-10, 06:10 PM
Things that are possible may have zero probability. For example, everyone has a weight, but the probability that your weight is exactly a given value is zero. The point being if you are selecting from a continuous distribution, any given choice has a zero probability - you can only meaningfully talk about probability of a value in some interval.

So does that mean that the probability of two arrows hitting a target at once is the same as with three?

CRGreathouse
Jul15-10, 06:17 PM
So does that mean that the probability of two arrows hitting a target at once is the same as with three?

A target has nonzero size, so no. But two arrows and three arrows would (under that model, at least) have probability 0 to hit the same point.

Dr Chaos
Jul15-10, 09:59 PM
A target has nonzero size, so no. But two arrows and three arrows would (under that model, at least) have probability 0 to hit the same point.

They don't have to hit the same point on the target - they just have to hit it at the exact same time.

CRGreathouse
Jul15-10, 10:56 PM
They don't have to hit the same point on the target - they just have to hit it at the exact same time.

Then yes, probability 0.