I have been assigned the following problem: Given numbers -25, 2, 3, 8, 10, 14, 18, 21, 32
You are told the mean of the numbers is 9.222 and the mean of their square is 309.666. What is the sample standard deviation?
The answer is given as $\sqrt{9/8 * (309.666-9.222^2)} =15.896$
This is a new way of calculating standard deviation to me. So I tried the old way I know with a spreadsheet in yellow. I get the answer as 44.92
What am I missing?
You need to divide $2021.556$ by $9-1=8$ before taking the square root.