Which one of the following is the standard deviation of the first 'n' natural number?
1
\(\sigma=\sqrt{\frac{1}{6}\left(n^2-1\right)}\)
2
\(\sigma=\sqrt{\frac{1}{6}\left(n^2+1\right)}\)
3
\(\sigma=\sqrt{\frac{1}{12}\left(n^2-1\right)}\)
4
\(\sigma=\sqrt{\frac{1}{12}\left(n^2+1\right)}\)