Bottles of water are labeled as containing 12 oz. Statistics students weighted the content of 7 randomly chosen bottles and found the mean weight to be 12.15 oz.

Question

Assume that bottles of water are filled so that the actual amounts are normally distributed with a mean of 12.00 oz. and a standard deviation of .09 oz. Find the probability that a sample of 7 cans will have a mean amount of at least 12.15 oz.

I took (12.15-12)/.09 and got 1.66666667. I took the value for 1.7 in the normal distribution table and got .9525. I entered that as my answer and it wasn't right, so I thought that maybe it was supposed to be 1-.9525, but that wasn't right either. Should the 7 cans somehow fit into this?

Answer 1

I used this page
http://davidmlane.com/hyperstat/z_table.html
and got the same result as you did after
1 - .9525

What answer are you supposed to get?

Answer 2

It's an online program that my homework is on, and it only tells you whether you're right or not. The more I thought about it, if the bottles have a mean of 12, they'll never have a mean of 12.15. I tried 0 and it came up correct.