00:01
For this question, we are told that on a certain flight, there are 19 seats available, and the airline made 22 reservations for these 19 seats.
00:11
We're also told that 13 of these reservations are for regular customers who are assumed to show up.
00:18
That means, of the remaining, there are nine other reservations that are not regular customers.
00:25
And we are told for that these people, their probabilities of showing up are 59%.
00:33
And so we're asked two questions.
00:34
The probability that an overbooking occurs and the probability that the flight has empty seats.
00:40
So let's first define a random variable x as the number of the nine non -regular customers who show up for the flight.
00:48
And here each of these nine can be thought of as bernoulli trials, either shows up or not.
00:54
And if we can assume that their outcomes are independent, then the number of successes in a fixed number of independent bernoulli trials is a binomial random variable.
01:04
So x is a binomial based on nine trials and probability of success .59.
01:12
So we already know that 13 are showing up.
01:14
We will have an overbooking if a total of 20 or more show up.
01:21
So that means a total of seven or more of the nine non -regular customers.
01:28
So that is we want to find the probability that x is at least seven.
01:36
This can be expressed as one minus the probability that x is at most to 6.
01:41
And we can use excel to solve this...