A rice retailer asserts that the average expiry of her Cindy Rice is 60 months. However, the expiry guarantee on this brand is for just 36 months. Suppose the standard deviation of the life length is known
to be 10 months, and the frequency distribution of the life-length data is known to be bell-shaped.
a. Approximately what percentage of the retailer’s grade A batteries will last more than 50
months, assuming the rice retailer’s assertion is true?
b. Approximately what percentage of the retailer’s Cindy Rice will last less than 40 months,
assuming the manufacturer’s claim is true?
c. Suppose her Cindy Rice lasts 37 months before expiry. What could you infer about the
retailer’s assertion?