... ẩ căn b c 2 c a ph ng saiậ ủ ươ•Moment h n h p c p 2: ỗ ợ ấ∫∞∞−=dx)t,x(xf)t(m11∫∞∞−=dx)t,x(fx)t(m1 2 2[ ])t(m)t(mdx)t,x(f)t(mx)t( 2 121 2 1 2 −=−=σ∫∞∞− 21 221 122 121 2dxdx)t,x,t,x(fxx)t,t(m∫ ... gian v i tr trung bình t p ồ ấ ị ờ ớ ị ậh pợ1im)t()t(=ξ=ξ 2 22 im)t()t(=ξ=ξ 2 1 2 2 2 mm)t(+σ==ξ)(mdxdx),x,x(fxx)(R)(R 22 121 221 iτ=τ=τ=τ∫∫∞∞−∞∞− Tín hi u ng u nhiên d ngệ ẫ ừTín ... •pdf c p 1 là h ng sấ ằ ố•pdf c p 2 là hàm m t bi nấ ộ ế)tt, ,tt,tt,x, ,x,x(f)t, ,t,t,x, ,x,x(fN21N21NN21N21N∗∗∗+++=)(m)t,t(m,)t(,)t(,m)t(m,m)t(m 22 12 2 22 11τ=σ=σσ=σ== Tr trung bình theo...