Question

A shipment of 10,000 bags of oranges arrives at a distribution center with a nominal weight of 3200 g per bag. A sample of 25 bags is selected and weighed. The average weight of the sample is 3300 g. From past shipments, it is known that the standard deviation of weight among cartons is 80 g. How many bags need to be sampled to ensure that the 95% confidence interval has a margin of error of 20 g?

a) 8 b) 15 c) 31 d) 62

Answer 1

Here z value is 1.96 as P(-1.96<z<1.96)=0.95

Further Margin of Error is E=20

Also standard deviation is given as 80

So we will find n using formula of E

So

Hence answer here is d. 62