00:01
We are using binomial probability to solve this question.
00:11
And when you're doing binomial probability, the probability can be found by using ncx times p to the x times q to the n minus x, where p represents the probability of success and q represents the probability of failure.
00:36
And n is the number of trials.
00:46
So for part a, we want to determine the probability that a single detection system will detect an attack.
00:58
So therefore, n would be one.
01:01
And the probability of success, we're assuming that a particular detection system has a 0 .90 probability.
01:11
So our probability of success is going to be 0 .90.
01:17
So that means the probability of failure is going to be 0 .10.
01:22
So the answer to this, what is the probability that a single detection? well, that would be 0 .90.
01:31
For part b, we're best to look at a chart.
01:37
So this time n is going to be 2.
01:39
P is going to be 0 .90.
01:41
Q is going to be 0 .10.
01:44
So let's look at all our possible outcomes.
01:51
We might have neither of the two detect the attack.
01:56
We might have one of the two detect the attack, or we might have both detect the attack.
02:03
So we're going to substitute the 0, the 1, and the 2 in place of the x's in our formula.
02:11
So in your calculator, you're going to do 2cx times 0 .9 or 0 .90 to the x times 0 .10 to the 2 minus x, and x will change from 0 to 1 to 2.
02:30
And in doing so, you'll get a 0 .01, a 0 .18, and 0 .81 .1...