If the average speed of all drivers on route 80 is 71 mph, stand. dev. is 6 mph what percentage of drivers:?

a) 75 mph or greater


b) 55 mph or less


c) 80 mph or greater


d) between 60 and 67 mph

If the average speed of all drivers on route 80 is 71 mph, stand. dev. is 6 mph what percentage of drivers:?
The answers for this can be found using the z-table for standard normal distribution. using the formula z= (x-mu)/sigma, you can find the z-score which correlates to the probability underneath the curve. The answers are as follows:





a) .2525


b) .004


c) .067


d) .219