The Polk Company reported that the average age of a car on U. S. roads in a recent year was 7.5 years. Suppose the distribution of ages of cars on U. S. roads is approximately bell-shaped. (a) If 99.7% of the ages are between 1 year and 14 years, what is the standard deviation of car age? (5 points) (b) Suppose

The standard deviation of car age is 2.17 years.

Step-by-step explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 7.5

(a) If 99.7% of the ages are between 1 year and 14 years, what is the standard deviation of car age?

This means that 1 is 3 standard deviations below the mean and 14 is 3 standard deviations above the mean.

So

I want to find

The standard deviation of car age is 2.17 years.

you answer is a

step-by-step explanation: