High School

A fitness company is building a 20-story high-rise. Architects building the high-rise know that women working for the company have weights that are normally distributed with a mean of 143 lb and a standard deviation of 29 lb, and men working for the company have weights that are normally distributed with a mean of 168 lb and a standard deviation of 34 lb.

You need to design an elevator that will safely carry 17 people. Assuming a worst-case scenario of 17 male passengers, find the maximum total allowable weight if we want a 0.995 probability that this maximum will not be exceeded when 17 males are randomly selected.

Maximum weight = _______ lb

Answer :

To find the maximum total allowable weight when 17 males are randomly selected, we need to consider the worst case scenario. In this case, we assume that all 17 passengers are males, and we want to calculate the maximum weight that has a 0.995 probability of not being exceeded.

The weight of each male passenger is normally distributed with a mean of 168 lb and a standard deviation of 34 lb. When summing the weights of multiple passengers, the sum follows a normal distribution as well. The mean of the sum is equal to the sum of the individual means, and the standard deviation of the sum is the square root of the sum of the individual variances.

Mean of the sum = Number of passengers * Mean of each passenger = 17 * 168 = 2856 lb

Standard deviation of the sum = sqrt(Number of passengers) * Standard deviation of each passenger = sqrt(17) * 34 ≈ 82.549 lb

Now, we need to find the maximum weight that has a 0.995 probability of not being exceeded. This is equivalent to finding the z-score

corresponding to a 0.995 cumulative probability.

Using a standard normal distribution table or a calculator, we find that the z-score for a cumulative probability of 0.995 is approximately 2.575.

To find the maximum allowable weight, we can use the formula:

Maximum allowable weight = Mean of the sum + (Z-score * Standard deviation of the sum)

Maximum allowable weight = 2856 + (2.575 * 82.549) ≈ 3087.018 lb

Therefore, the maximum total allowable weight, with a 0.995 probability of not being exceeded when 17 males are randomly selected, is approximately 3087.018 lb.

Learn more about statistics here:

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