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An airline estimates that among the plane tickets it sells, 5% of the customers do not show up. Aiming to take advantage of this the airline sells 80 tickets for a plane with 78 seats. What is the probability that nobody will be denied boarding? Find the exact value and an estimate, using the law of small numbers.

User Tedski
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Final answer:

To find the probability that nobody will be denied boarding, we can use the binomial probability formula. We can also estimate the probability using a normal approximation to the binomial distribution. The exact probability can be calculated using the formula, while the estimated probability can be found using the normal distribution.

Step-by-step explanation:

To find the probability that nobody will be denied boarding, we can use the binomial probability formula. The formula is:

P(X = k) = C(n, k) * p^k * (1-p)^(n-k)

Where:



  • P(X = k) is the probability of getting exactly k successes
  • C(n, k) is the number of combinations of n items taken k at a time
  • p is the probability of success on a single trial
  • n is the number of trials



In this case, we want to find the probability of getting exactly 0 customers who don't show up. So k = 0. The number of combinations of 80 tickets taken 0 at a time is simply 1. The probability of a customer not showing up is 0.05, so p = 0.05. And the number of trials is 80.

Using the formula:

P(X = 0) = C(80, 0) * 0.05^0 * (1-0.05)^(80-0)

P(X = 0) = 1 * 1 * 0.95^80

Calculating this value yields the exact probability that nobody will be denied boarding. To estimate the probability using the law of small numbers, we can use a normal approximation to the binomial distribution. The mean of the binomial distribution is np and the standard deviation is sqrt(np(1-p)). In this case, n = 80 and p = 0.05.

The mean of the binomial distribution is 80 * 0.05 = 4, and the standard deviation is sqrt(80 * 0.05 * (1-0.05)) = 1.8. Since we are looking for the probability that nobody will be denied boarding (0 customers not showing up), we can use the normal distribution to estimate this probability as:

P(X = 0) = P(Z < (0.5 - 4) / 1.8)

Calculating this value using the standard normal table or a calculator gives us the estimated probability.

User Shane Haw
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