00:01
Here we have a system that works only if there is a pathway from left to right that is successfully working.
00:09
And we are given the probabilities that the individual components work.
00:14
Probability that component one works is .78.
00:18
For component 2, that's .77.
00:24
3 is .86, and 4 is .85.
00:35
So for part a, we want the probability that the system works.
00:39
Now the system is going to work if component one works, or if component two works, or if three and four work, or some combination of those three scenarios.
00:52
So mathematically we can write it like this.
01:15
Now perhaps for simplicity, let's call these events a, b, and c.
01:24
So c is components three and four working.
01:31
So this is the probability of a or b or c.
01:37
And using our basic probability axiom, this is the probability of a, plus the probability of b, plus the probability of c, minus the probability of a and b, minus the probability of a and c, minus the probability of b and c, plus the probability of a and b and c.
02:13
So the probability of a is simply the probability of 1.
02:24
Probability of b is the probability of 2.
02:28
And the probability of c is, maybe i'll use another color for this...