Question

A snow tire manufacturer believes that a typical set of snow tires lasts on average for 30,000 miles. They also believe that 95% of drivers get between 20,000 and 40,000 miles of use from the tires. What value of σ, the standard deviation, would be needed to make the information above approximately consistent with a Normal distribution model for tire wear? You should use the Empirical Rule to answer this question.

You should use the Empirical Rule to answer this question.

1 point

20,000

10,000

3,333

5,000

Answer 1

Given a snow tyre manufacturer believe that a typical set of snow tires last on average for 30,000 miles.

They also believe that 90% of drivers gets between 20000 and 40,000 miles of use from the tires.

According to the Empirical rule, for a symmetric distribution approximately 95% of observations lies within 2 standard deviation of the mean.

Thus we have,

Therefore the value of standard deviation would be needed to make the information consistent with a Normal distribution model for tire wear is