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1. ### Please help with the following question

Okay, thank you. Is my calculation of the standard deviation above correct?
2. ### Please help with the following question

Can you please provide the formula? I just used the z-score of 1.96 for a 99% confidence interval to calculate the standard deviation, then used that to solve for the subsequent z-score and associated p-values.
3. ### Please help with the following question

Yes, here are my answers for the first two questions: 2. How probable is it that such a chain has a total length between 900 and 1100? .95 3. How probable is it that such a chain has a total length between 990 and 1010? .0796

.51 = s.d
5. ### Please help with the following question

Is the probability between just 95% for chains between 9 and 11? I'm not sure how to approach without standard deviation.
6. ### Please help with the following question

A firm produces chains. The length of each link is independent of each other and normally distributed. The mean length of a link is 10. 95% of all links have a length between 9 and 11. The total length of each chain is the sum of the lengths of its links. You consider chains with 100 links 2...