X ∼ π ( λ ) X\sim \pi(\lambda) X∼π(λ)
F X ( x ) = e − λ ∑ i = 0 ∣ x ∣ λ i i ! F_X(x) = e^{-\lambda}\sum\limits_{i=0}^{|x|}\frac{\lambda^i}{i!} FX(x)=e−λi=0∑∣x∣i!λi
f X ( k ) = λ k k ! e − λ f_X(k)=\frac{\lambda^k}{k!}e^{-\lambda} fX(k)=k!λke−λ
E ( X ) = λ E(X)=\lambda E(X)=λ
D ( X ) = λ D(X)=\lambda D(X)=λ
2018/12/07