Question 1089939: Suppose the mileage 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. 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 standard deviation and 96% for 2 standard deviation). How many cars would have mileages between 30,000 and 40,000?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! The mean is 30K with sd of 5 K
z=(x-mean)/sd, and this is a z of +/-1
That is 68% of them or 680 cars.
Between 30 and 40 K is between 0 and 2 sds
But 96% applies to +/- 2 sd s so 48% between 0 and 2 sd s and 48% between 0 and -2 sd s. Only the first 48% applies. That is 480 cars.
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