00:01
If you are given a counting tree such as this labeled with the various probabilities, how can we then find these probabilities from that tree diagram? so the first thing is to understand some of the symbolism in these probability statements.
00:23
So this, we would say in words, the probability of c given a, meaning what's the probability that we're going to end up right here at c given we follow the path for a? so if you think about that statement, they're saying, what is the probability that we're going to end up here? and the probability we're going to end up here is 0 .4.
00:50
So the second question, what's the probability of d given we follow path b.
00:55
And if you follow path b to d, you see that d has that probability of 0 .45.
01:04
Whenever you see this symbol in probability, it means intersects.
01:09
So the probability that a intersects c, meaning that we have to follow both paths, that we have to put them together.
01:18
So we're going to multiply.
01:20
So the probability of a is 0 .2.
01:23
The probability of c is 0 .4, and when we multiply the two together, we get a probability of 0 .08.
01:32
So following that same process, the probability of b is 0 .8.
01:39
The probability of d is 0 .45...