00:01
For this question, we refer back to exercise 30 in section 2 .3, where we had the probability mass function for the number of traffic citations for randomly selected people.
00:15
And now we answer a few questions about the probabilities of numbers of people who have no citations or at least one citation.
00:25
So the important thing from exercise 30 in section 2 .3 was that the probability of getting no citations was 0 .6.
00:36
So we will call that a success in this binomial distribution.
00:44
And now we're picking 15 randomly selected people and assessing how many of them have no citations or have at least one citation.
00:57
So for a we're asked what is the probability that at least 10 have no citations? so that is the probability that the number of successes is at least 10 and this is equal to 1 minus the probability of at most 9 successes, which is equal to 1 minus the cumulative probability of 9 successes, given these binomial parameters.
01:42
And this comes out to 0 .403.
01:49
And then for b were asked, what is the probability that fewer than half have at least one citation, which also is the same as saying, what is the probability that a probability that a probability that a number of half have? at least half have no citations.
02:10
So our sample size is 15...