A mill packs flour in “25 lb” sacks. Its quality control inspectors check the process by randomly selecting 20 sacks each hour and recording their weights. The weights of the latest sample have a mean of 25.45 lbs and a standard deviation of 0.80 lbs. a. Construct a 95% confidence interval estimate for the average weight of all such 25 lb sacks. b. Change the interval above to a 99% confidence interval estimate for the average weight of all such sacks.  c. If they want this 99% confidence interval to be no wider than ± ¼ lb, by how much must they increase their sample?

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