Can you provide the correct mathematical formula to achieve a clear understanding of "A student randomly selects 10 CDs at a store. The mean is $13.75 with a standard deviation of $1.50. Construct a 95% confidence interval for the population standard deviation, ?"

Despite receiving the following response: "ok I did some digging in my old statistics work. The formula for confidence interval is X Z s/n. X is the mean, Z is the z-score, s is the standard deviation, and n is the sample. So that would read 13.75 1.96(1.50/10). When you work that formula with a calculator you get .930. So it would be 12.82 and 14.68. Let me know if this helps. Sorry for the confusion."

If we follow your suggestion with a calculator, we get the following:

13.75+ 1.96x(1.50 divided by the square root of 10)

=7.46

and

13.75 - 1.96x(1.50 divided by the square root of 10)

=5.60

Thus, how do you come up with .930 ?