或 σ 2 = ∑ x 2 p ( x ) − μ 2 {\displaystyle \sigma ^{2}=\sum {x^{2}p(x)-\mu ^{2}}}
P ( X ≤ x | n , p > .50 ) = P ( X ≥ n − x | n , 1 − p ) {\displaystyle P(X\leq x|n,p>.50)=P(X\geq n-x|n,1-p)} P ( X ≥ x | n , p > .50 ) = P ( X ≤ n − x | n , 1 − p ) {\displaystyle P(X\geq x|n,p>.50)=P(X\leq n-x|n,1-p)}