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It is estimated that 3.5% of the general population will live past their 90th birthday. In a graduating class of 792 high school seniors, find the following probabilities. (Round your answers to four decimal places.)

(a) 15 or more will live beyond their 90th birthday
(b) 30 or more will live beyond their 90th birthday
(c) between 25 and 35 will live beyond their 90th birthday
(d) more than 40 will live beyond their 90th birthday

1 Answer

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Final answer:

The question involves using binomial probabilities to estimate the number of people in a graduating class who will live past their 90th birthday. Large sample sizes justify the use of a normal approximation instead of the binomial formula. Calculating the probabilities for specific scenarios necessitates using a binomial coefficient or employing a cumulative distribution function.

Step-by-step explanation:

The question involves calculating probabilities using the estimated percentage of individuals in a given population who will live past their 90th birthday. We are working with a graduating class of 792 high school seniors, and given the estimate that 3.5% of the general population will live past their 90th birthday, we can treat each part of the problem as a binomial probability scenario, where n = 792 and p (the probability of success, which in this case is living past 90) is 0.035.

To find the probabilities for each scenario, we could use the formula for a binomial probability P(X = k) = (n choose k) * p^k * (1-p)^(n-k), where (n choose k) is a binomial coefficient. However, because the sample size is large, we'd typically use a normal approximation to the binomial distribution. The normal approximation involves finding the mean μ = np and variance σ^2 = np(1-p), and thus the standard deviation σ. We'd then use these parameters to find the z-scores corresponding to the various probabilities we're trying to calculate.

However, bear in mind that finding exact probabilities for more than or between certain values would require a cumulative distribution function (CDF) for the binomial or its normal approximation, which could be found using a statistical software or calculator with such functionality.

User Greg Bacchus
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