15, 16, 16, 15, 19, 16, 18, 15, 17,16, 15,17,16, 18

I found the mean family size which is 16.4. To find the mean family size, I added up all of the numbers listed above and divided the total by 14. That gave me 16.35714286 which I rounded to 16.4. I'm stuck on part B.

b. What is the standard deviation for the sample? (Round to the nearest tenth)