In: Statistics and Probability
The speed limit of a road is 65 miles per hour. The speed of a car on the highway follows a normal distribution with a mean of 70 and standard deviation of 5. What percent of the distribution breaks the speed limit?
The speed limit of a road is 65 miles per hour. The speed of a car on the highway follows a normal distribution with a mean of 70 and standard deviation of 5. A police officer will only react to speeding if the person is going 3 standard deviations above the average (z = 3). What is the speed at which he will react?
Solution:
Given: The speed of a car on the highway follows a normal distribution with a mean of 70 and standard deviation of 5.
The speed limit of a road is 65 miles per hour.
Part a) What percent of the distribution breaks the speed limit?
That is find:
P( X> 65) =..........?
Find z score for x = 65
Look in z table for z = -1.0 and 0.00 and find corresponding area.
P( Z< -1.00 ) = 0.1587
thus
Thus 84.13% of the distribution breaks the speed limit.
Part b) A police officer will only react to speeding if the person is going 3 standard deviations above the average (z = 3).
What is the speed at which he will react?
Use following formula to find x value:
miles per hour.
The speed at which a police officer will react is 85 miles per hour.