If X & Y are independent variables, then S.D (X-Y) = ….. |

If X & Y are independent variables, then S.D (X-Y) = …..:


	$S . D (X) + S . D (Y)$
	$S . D (X) - S . D (Y)$
	$\sqrt{V a r (X) + V a r (Y)}$
	$\sqrt{V a r (X) - V a r (Y)}$