Question

An elevator has a placard stating that the maximum capacity is 1296 lb long dash — 8 passengers.​ So, 8 adult male passengers can have a mean weight of up to 1296 divided by 8 equals 162 pounds. 1296/8=162 pounds. If the elevator is loaded with 8 adult male​ passengers, find the probability that it is overloaded because they have a mean weight greater than 162 lb.​ (Assume that weights of males are normally distributed with a mean of 170 lb and a standard deviation of 29 lb​.) Does this elevator appear to be​ safe?

Answer 1

Answer:

There is a 98.26% probability that it is overloaded.

This elevator does not appear to be safe.

Step-by-step explanation:

Problems of normally distributed samples can be solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$, the zscore of a measure X is given by

$Z = \frac{X - \mu}{\sigma}$

After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X. Subtracting 1 by the pvalue, we This p-value is the probability that the value of the measure is greater than X.

In this problem, we have that:

Assume that weights of males are normally distributed with a mean of 170 lb, so $\mu = 170$

They have a standard deviation of standard deviation of 29 lb, so $\sigma = 29$.

We have a sample of 8 adults, so we have to find the standard deviation of the sample to use in the place of $\sigma$ in the Z score formula.

$s = \frac{\sigma}{8} = \frac{29}{8} = 3.625$

Find the probability that it is overloaded because they have a mean weight greater than 162 lb, so $X = 162$

$Z = \frac{X - \mu}{\sigma}$

$Z = \frac{162 - 170}{3.625}$

$Z = -2.21$

$Z = -2.21$ has a pvalue 0.0174.

So, there is a 1-0.0174 = 0.9826 = 98.26% probability that it is overloaded.

Any probability that is above 95% is considerer unusually high. So, this elevator does not appear to be safe, since there is a 98.26% probability that it is overloaded.