Question

投掷一颗骰子的点数为X E(X)=3.5 则D(X)

Answer 1

E(x)=1/6(1+2+3+4+5+6)=3.5

E(x²)=1/6(1²+2²+3²+4²+5²+6²)=91/6

D(x)=E(x²)-(E(X))²=91/6-3.5²=2.917