00:01
A plane is missing and is presumed to have equal probability of going down in any of three regions.
00:06
If a plane is actually down in region i, let 1 minus alpha denote the probability that the plane will be found upon a search of the ith region, with i being 1, 2, or 3.
00:17
What is the conditional probability that the plane is in? and then we have three things that we're going to look at.
00:22
But first, let's let f complement 1 represent being unsuccessful.
00:35
In region one.
00:39
So for a, and the reason why i'm doing that is because that's a part of a, b, and c is unsuccessful in the search of region one.
00:48
So for a, we're finding the probability that the plane was in region one, given f, the complement of f sub one.
01:01
So we do the probability of f, the complement sub one, given region one, times the probability, let's see, i don't like that, there you go, probability of region 1 and we're going to take that over the sum of our three regions so what that looks like is the probability of f complements of 1 given 1 times the probability of 1 plus the probability of f complements of one region 2 times the probability of region 2 plus the probability of f complements of one region three times the probability of region three.
01:50
So what that actually is going to equal for our top is using the information they told us.
01:56
So let if a plane is actually down in region i, let one minus alpha denote the probability of the plane will be found.
02:04
So we're going to do one minus one minus alpha for region one or alpha sub one.
02:11
And the bottom is going to be one minus one.
02:15
Minus alpha sub 1.
02:17
And the other thing we should know is that the probability of f complement sub 1 given 2 is the same as the probability of f complement sub 1 region 3, and all each of those are equal to 1...