泊松分布：P{X=k}=λ^k·exp(-λ)/k!(k=0,1,2,...λ>0)E(X)=∑kP{X=k}=∑λ^k·exp(-λ)/(k-1)!(k从1到+无穷)由泰勒展式有exp(λ)=∑λ^k/k!(k从0到+无穷)=∑λ^(k-1)/(k-1)!(k从1到+无穷)代入上式得E(X)=λexp(λ)e...