文档介绍：概率统计大作业参考解答第三章多维随机变量及其分布一、填空题:,;;;;.;?.;;??A;2??B;)1)(4(2),(222yxyxf????.二、选择题:A;C;D;C;D;A;、解答题::(1)(X,Y)的分布律及边缘分布律为:YX1?0?????iPiXP1?858186124524182??jPjYP???65611(2)??YXP?=P{Y=-1}+P{X=1,Y=0}=24165?=2421.(3)Z1?:(1)X与Y的所有可能取值均为2,1,0,联合分布为YX0120413191161910236100(2))0()0,1()01(??????ZPZXPZXP94)21(6261212???:(1)由,31),(1010kkxdydxdxdyyxfx???????????????得3?k.(2)???????????????????????其他,010,030),()(00xdyxdydydyyxfxfxxX??????其它,010,32xx;同理:?????????其他,010),1(23)(),()()(yxfyfxfYX?,故X与Y不是相互独立的.(3)????????1),(}1{yxdxdyyxfYXP8531211????:),(,211YXdxxSDeD????的面积为的联合概率密度为:???????其他,0),(,21),(Dyxyxf从而????????????????其他,01,2121),()(210exxdydyyxfxfxX,.41)2()(2????XXfxfx处,:(1)????????????????000),()(0xxdyedyyxfxfxxX???????000xxxex?????????其他001)(),()|(|xyxxfyxfxyfXXY;(2)???????0,00,)(yyeyfyY,)1()1,1()11(??????YPYXPYXP1211100?????????:利用公式dxxzxfzfZ???????),()(,?????????????其他010,10)(2),(xzxxzxxzxf??????????其他01,102zxzxz.①当0?z或2?z时,0)(?zfZ;概率统计大作业参考解答②当10??z时,)2()2()(0zzdxzzfzZ?????;③当21??z时,211)2()2()(zdxzzfzZ??????.故YXZ??.的概率密度为????????????其他021)2(10)2()(:、填空题:;;(-3,25);;,2;;?;;;、选择题:D;B;C;B;B;A;D;D;A;、解答题:( )21(| |) | |2xE x x e dx???