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I am not too familiar with how to post a question in this forum but i have a cqe exam on this coming saturday and i am desperately looking for a solution to the following problem. Can anyone help me out? May be even post this question at the right place???

Compute the upper control limit for an s chart, based on a sample size of 10, if the process is in control with a mean of 40 and a sample standard deviation of 7.

A. 11.7 B. 13.3 C. 15.7 D. 21Answer is A ... but i dont know how do u calculate it??

Please help!

Thanks,