00:01
So for this problem, to begin, we know that we're told to treat x as a binomial random variable, where n is some value, which is changing throughout the problem.
00:12
And the probability of success is 0 .89.
00:14
Also, we have the probability distribution function for a binomial given here.
00:18
N choose k times p to the power of k, times 1 minus p to the power of n minus k.
00:23
So for part a, the probability of an individual detection system detecting an attack, well, that probability is just given to us as 0 .89.
00:35
Then, for part b, we're looking for the probability that x is greater than or equal to 1.
00:42
Or we can think of that as 1 minus the probability that x equals 0.
00:49
Probability that x equals 0, that would be n -chus 0, which is just 1 times p to the power of 0, which is just 1, times 1 minus p, which is 0 .11, to the power of 2.
00:59
So, oh, pardon me, i need to be careful here, it's one minus all of that...