Statitistics: Estimating the population mean when the standard deviation is known:  I am not sure which n to use in the formula for the confidence interval equation:
 x +/- z*(standard deviation/sqrt(n))
 If we have data of ten people, and if we have the data of ten sets of ten people each, what is the difference in the n that we use? What is the difference between the standard deviation and the standard error? Are we using the number of sampling means or just the number of samples?