P(甲射中0次)=0.2^3=0.008
P(甲射中1次)=C(3,1)*0.8*0.2^2=0.096
P(甲射中2次)=C(3,2)*0.8^2*0.2=0.384
P(甲射中3次)=0.8^3=0.512
P(乙射中0次)=0.1^2=0.01
P(乙射中1次)=C(2,1)*0.9*0.1=0.18
P(乙射中2次)=C(2,2)*0.9^2=0.81
甲乙獨(dú)立,則聯(lián)合分布等于邊際分布的積,
P(甲射中0次,乙射中0次)=0.00008
P(甲射中0次,乙射中1次)=0.00144
P(甲射中0次,乙射中2次)=0.00648
P(甲射中1次,乙射中0次)=0.00096
P(甲射中1次,乙射中1次)=0.01728
P(甲射中1次,乙射中2次)=0.07776
P(甲射中2次,乙射中0次)=0.00384
P(甲射中2次,乙射中1次)=0.06912
P(甲射中2次,乙射中2次)=0.31104
P(甲射中3次,乙射中0次)=0.00512
P(甲射中3次,乙射中1次)=0.09216
P(甲射中3次,乙射中2次)=0.41472邊緣概率分布呢