Suppose the mileages of the cars in a randomly selected parking lot follow the normal distribution. 1,000 cars in the parking lot are surveyed and the average or mean mileage is 30,000 on those cars. If the standard deviation is 5,000, how many cars would fall in the range of mileage of 25,000 to 35,000 approximately? (use 68% for the 1 SD coverage and 96% for 2 SD)

Question

anonymous · Answer

In the previous problem, how many cars approximately would have mileages between 30,000 and 40,000?

kropot72 · Answer

The percentage of mileages that fall within the range of plus and minus one standard deviation from the mean is approximately 68%. Therefore the number of cars that would fall in the range of mileage of 25,000 to 35,000 is approximately 68% of 1000.
The percentage of mileages that fall within the range of plus two standard deviations from the mean is approximately 96/2 = 48%. Therefore the number of cars that would fall in the range of mileage of 30,000 to 40,000 is approximately 48% of 1000.