Question

某人投篮的命中率为0.4,投篮两次,求：（1）计算投进球数的数学期望和方差

Answer 1

投中0次 P1 0.6*0.6=0.36

一次P2 0.480.6*2=0.48

两次P3 0.4*0.4=0.16

E(x)=0*0.36+1*0.48+2*0.16=0.8

E(x^2)=0*0.36+1*0.48+4*0.16=1.12

D(x)=E(x^2)-E(x)=1.12-0.8=0.32