Question

Suppose that the speeds of cars travelling on California freeways are normally distributed with a mean of miles/hour. The highway patrol's policy is to issue tickets for cars with speeds exceeding miles/hour. The records show that exactly of the speeds exceed this limit. Find the standard deviation of the speeds of cars travelling on California freeways. Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.

Answer 1

the standard deviation of the speeds of cars travelling on California freeways is 6.0 miles per hour

Explanation:

The computation of the standard deviation of the speeds of cars is shown below;

The z score for the top 1% is 2.326

So,

= (75 - 61) ÷ standard deviation = 2.326

Standard deviation is

= 14 ÷ 2.326

= 6.0 miles per hour

Hence, the standard deviation of the speeds of cars travelling on California freeways is 6.0 miles per hour