I’m working my way through the appendix of THE BOOK and I’m stuck. Here’s my problem…

In the section on Uncertainty, there’s an equation for uncertainty in variance:
Variance / sqrt(2/N)

OR…

4.5 / sqrt(2/5)
4.5 / sqrt(0.4)
4.5 / 0.63
7.1

For the value series given (0, 0, 2, 3, 5) the result should be 2.85.

I can get 2.85 if I follow the formula for uncertainty in standard deviation but use Variance but multiple the result by 2:

4.5 / sqrt(2*n)
4.5 / sqrt(2*5)
4.5 / 3.16
1.42 x 2 = 2.85

The above worked but that doesn’t make it correct. Where did I go wrong?