00:01
So we're given the probability of a sub 1 is equal to 0 .5.
00:05
Probability of b sub 1 given a sub 1 is equal to 0 .4.
00:11
And the probability of b sub 1 given a sub 2 is equal to 0 .7.
00:19
And we want to end up finding the probability of a sub 1 given b sub 2.
00:25
That's what we want to find.
00:26
So let's make our chart.
00:31
And again, we will be assuming that a1 and a2 are complementary events, and b1 and b2 are complementary events.
00:41
So if we know that the probability of a sub 1 is 0 .5, that means the probability of a sub 2 is also 0 .5, and that these two have to add to 1.
00:53
And that's all we know, other than these two conditionals.
00:57
So let's do some figuring.
00:59
So first of all, we're going to use this conditional, and we know that this conditional means the probability of b1 and a sub 1 divided by the probability of a sub 1...