Rochester, New York averages =21.9 inches of snow for the month of December. The

Question

Rochester, New York averages =21.9 inches of snow for the month of December. The distribution of snowfall amounts is approxiamtely normal with a standar deviation of =6.5 inches. This year a local jewelry store is advertising a refund of 50% of all purchases made in December, if the accumulated snowfall by the end of the month falls within the top 10% of the distribution. What is the probability that the jewelry store will have to pay off on its promise? How many inches of snow actually have to fall?

Explanation / Answer

mean is 21.9 and s is 6.5

z is calculated as (x-mean)/s

for top 10% of distribution, we need to find the z value at 90% of distribution which is calculated from normal distribution table as 1.28

thus the value is 21.9+6.5*1.28 =30.22

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