posted by Fran .
You are a buyer bidding on a lot of 10,000 uncut diamonds. You select 100 stones at random, sight unseen, from the lot. The average weight is 0.98 ct with a standard deviation in the sample of 0.11 ct. What is the 95% confidence interval for the average weight of a stone in the lot?
CI95 = mean + or - 1.96(sd/√n)
Substituting the data given in the problem:
CI95 = 0.98 + or - 1.96(0.11/√100)
I'll let you take it from here.