# Error analysis for uniform quantization of uniform input

I was told that

error energy $$\delta^2_e=\Delta^2/12,\quad \Delta=(B-A)/2^R$$ signal energy $$\delta^2_x = (B-A)^2/12$$ Here signal bounded:$$A\le x[n]\le B.$$ $$[A,B]$$ is split into $$2^R$$ subintervals.

But i don't understand how the signal energy was derived. More precisely, i don't understand why signal energy equals to variance.

EDIT: Ah, probably because we center signal around $$\frac{B-A}{2}$$.