I found out that the Standard Deviation is also equal too: f(x) Blue[br][br]which is the Normal Curve without Sigma in the Denominator!![br][br][br]Notice f(x) equation in Blue [br][br]Probabilities are found by Integrating f(x) from 1 to 2 and then dividing by the Standard Deviation ; f(x) / Std.

See what happen now above