【简答题】【消耗次数:1】
已知E(X)=1,E(Y)=2,E(XY)=3,则X,Y的协方差Cov(X,Y)=[填空]
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相关题目
【简答题】 已知E(X)=1,E(Y)=2,E(XY)=3,则X,Y的协方差Cov(X,Y)=[填空]
【单选题】 已知E(X)=1,E(Y)=2,E(XY)=3,则X,Y的协方差Cov(X,Y)=( )
①  2
②  1
③  0
④  3
【简答题】 已知E(X)=1,E(Y)=2,E(XY)=3,则X,Y的协方差Cov(X,Y)=[填空1]
【单选题】 对于任意两个随机变量X和Y,若E(XY)=E(X)E(Y),则
①  <img class=jc-formula data-tex=D(XY)=D(X)\cdot D(Y) src=https://huaweicloudobs.ahjxjy.cn/2CBC13536F3D454383026FC824D40897.png style=vertical-align: middle;/>
②  <img class=jc-formula data-tex=D(X+Y)=D(X)+D(Y) src=https://huaweicloudobs.ahjxjy.cn/F89D994387B840DDF2888C89E430CDB0.png style=vertical-align: middle;/>
③  X和Y独立
④  X和Y不独立
【简答题】 实数集合里,F(x,y): x=y, G(x,y): xy。公式“xy(G(x,y) ??F(x,y))”的真值:[填空1]
【简答题】 实数集合里,a =0,f (x,y)=x-y,F(x,y): x=y, G(x,y): xy。公式“xy(G(x,y) ??F(f(x,y),a))”的真值:[填空1]
【简答题】 自然数里,a=2,f (x,y)=x+y,g (x,y)=x·y,F (x,y): x=y。公式“xy(F(f(x,a),y) ?F(f(y,a),x))”的真值:[填空1]
【单选题】 设(X,Y)为二维随机向量,D(X)=16,D(Y)=25,ρXY=0.6,则Cov(X,Y)=( )
①  12
②  20
③  3
④  8
【单选题】 设(X,Y)为二维随机向量,D(X)=16,D(Y)=25,ρXY=0.6,则Cov(X,Y)=( )
①  12
②  20
③  8
④  3
【判断题】 设X、Y是随机变量,若X与Y相互独立,则E(XY)=EX?EY
①  正确
②  错误
随机题目
【单选题】 I am unhappy because she accepted my invitation _______ .
①  passively
②  extremely
③  undoubtedly
④  unwillingly
【单选题】 It’s getting late and I have to leave now.____________
①  So soon! I hope youve enjoyed it.
②  Have a cup of tea.
③  Not at all.
④  How about a cup of coffee?
【单选题】 You can experience a fast internet connection in()the same way as you do in the office.
①  more
②  much
③  better .
④  most
【单选题】 Nothing can prevent him _____ learning Chinese painting.
①  from
②  by
③  out
④  in
【单选题】 Thank you ever so much for the scarf you bought me.____________
①  No thanks.
②  No, it’s not so good.
③  I’m glad you like it.
④  Please don’t say so.
【单选题】 found a __________
①  corporation
②  company
③  machine
④  firm
【单选题】 Everybody likes her because she is always _______ .
①  Everybody likes her because she is always _______ .
②  cheerful
③  sad
④  selfish
【单选题】 It is the general manager who makes the _______decisions in business.
①  beginning
②  finishing
③  first
④  final
【单选题】 Those gifts o rare books that were given t us were deeply _____.
①  appreciated
②  approved
③  appealed
④  applied
【单选题】 Haven’t seen you for ages! What are you busy doing now?____________
①  I hate the weather here.
②  My hair is getting a bit longer.
③  I am working part time in a bookshop, you know.
④  Yeah, thanks for coming.