When is $YE(Ymidmathcal{G}) = E(Y^2midmathcal{G})$?Is it true that $E[|Y|mid{mathcal G}]leq |Y|$ almost...

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When is $YE(Ymidmathcal{G}) = E(Y^2midmathcal{G})$?


Is it true that $E[|Y|mid{mathcal G}]leq |Y|$ almost surely?How to prove that $E(Xmidsigma,(mathcal{G},mathcal{M}))=E(Xmidmathcal{M})$ if $mathcal{G}$ is independent of $X$ and $mathcal{M}$?Does $text E[text E[Xmidmathcal F]midmathcal G]=text E[text E[Xmidmathcal G]midmathcal F]$ hold when $mathcal Gnotsubseteqmathcal F$?Trying to understand $mathbb E[Xmid mathcal F]$ and Martingale conceptProving if $X$ if an $mathcal{F}$ measurable Random variable with $E(X) < infty$, then $E(Xmid mathcal{F}) = X$ a.e.When does $mathbf{E}(XYmidmathcal{A})=Xmathbf{E}(Ymidmathcal{A})$ hold?When “sure” property is equivalent to “almost sure” property?What does $mathbb P{X>xmid mathcal A}$ mean?Product measure : difference between $mathcal Mtimes mathcal M$ and ${Atimes Bmid A,Bin mathcal M}$how to prove $mathbb{E}[UVmid mathcal{B} ] = Umathbb{E}[Vmid mathcal{B} ]$ if $U$ is $mathcal{B}$-measurable?













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$begingroup$


I know this is true when $Y in mathcal{G}$, but is there a better (less restrictive) condition that can allow this?



In particular, I want to know when I can say that $E(YE(Ymidmathcal{G})) = E(E(Y^2midmathcal{G}))$, which is, of course, equal to $EY^2$.










share|cite|improve this question











$endgroup$

















    1












    $begingroup$


    I know this is true when $Y in mathcal{G}$, but is there a better (less restrictive) condition that can allow this?



    In particular, I want to know when I can say that $E(YE(Ymidmathcal{G})) = E(E(Y^2midmathcal{G}))$, which is, of course, equal to $EY^2$.










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      I know this is true when $Y in mathcal{G}$, but is there a better (less restrictive) condition that can allow this?



      In particular, I want to know when I can say that $E(YE(Ymidmathcal{G})) = E(E(Y^2midmathcal{G}))$, which is, of course, equal to $EY^2$.










      share|cite|improve this question











      $endgroup$




      I know this is true when $Y in mathcal{G}$, but is there a better (less restrictive) condition that can allow this?



      In particular, I want to know when I can say that $E(YE(Ymidmathcal{G})) = E(E(Y^2midmathcal{G}))$, which is, of course, equal to $EY^2$.







      probability probability-theory measure-theory






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Mar 20 at 13:10









      StubbornAtom

      6,30831440




      6,30831440










      asked Mar 20 at 13:07









      jackson5jackson5

      669513




      669513






















          1 Answer
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          $begingroup$

          No.



          If I understand correctly your notation, then $Yinmathcal{G}$ means that $Y$ is measurable with respect to $mathcal{G}$. In particular you have $E(Y|mathcal{G}),E(Y^2|mathcal{G})inmathcal{G}$.



          But then, from the equation $YE(Y|mathcal{G}) = E(Y^2|mathcal{G})$ you necessarily have that $Yinmathcal{G}$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Yes, that makes perfect sense. Thanks!
            $endgroup$
            – jackson5
            Mar 20 at 13:35












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          $begingroup$

          No.



          If I understand correctly your notation, then $Yinmathcal{G}$ means that $Y$ is measurable with respect to $mathcal{G}$. In particular you have $E(Y|mathcal{G}),E(Y^2|mathcal{G})inmathcal{G}$.



          But then, from the equation $YE(Y|mathcal{G}) = E(Y^2|mathcal{G})$ you necessarily have that $Yinmathcal{G}$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Yes, that makes perfect sense. Thanks!
            $endgroup$
            – jackson5
            Mar 20 at 13:35
















          5












          $begingroup$

          No.



          If I understand correctly your notation, then $Yinmathcal{G}$ means that $Y$ is measurable with respect to $mathcal{G}$. In particular you have $E(Y|mathcal{G}),E(Y^2|mathcal{G})inmathcal{G}$.



          But then, from the equation $YE(Y|mathcal{G}) = E(Y^2|mathcal{G})$ you necessarily have that $Yinmathcal{G}$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Yes, that makes perfect sense. Thanks!
            $endgroup$
            – jackson5
            Mar 20 at 13:35














          5












          5








          5





          $begingroup$

          No.



          If I understand correctly your notation, then $Yinmathcal{G}$ means that $Y$ is measurable with respect to $mathcal{G}$. In particular you have $E(Y|mathcal{G}),E(Y^2|mathcal{G})inmathcal{G}$.



          But then, from the equation $YE(Y|mathcal{G}) = E(Y^2|mathcal{G})$ you necessarily have that $Yinmathcal{G}$.






          share|cite|improve this answer









          $endgroup$



          No.



          If I understand correctly your notation, then $Yinmathcal{G}$ means that $Y$ is measurable with respect to $mathcal{G}$. In particular you have $E(Y|mathcal{G}),E(Y^2|mathcal{G})inmathcal{G}$.



          But then, from the equation $YE(Y|mathcal{G}) = E(Y^2|mathcal{G})$ you necessarily have that $Yinmathcal{G}$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Mar 20 at 13:29









          YankoYanko

          8,3842830




          8,3842830












          • $begingroup$
            Yes, that makes perfect sense. Thanks!
            $endgroup$
            – jackson5
            Mar 20 at 13:35


















          • $begingroup$
            Yes, that makes perfect sense. Thanks!
            $endgroup$
            – jackson5
            Mar 20 at 13:35
















          $begingroup$
          Yes, that makes perfect sense. Thanks!
          $endgroup$
          – jackson5
          Mar 20 at 13:35




          $begingroup$
          Yes, that makes perfect sense. Thanks!
          $endgroup$
          – jackson5
          Mar 20 at 13:35


















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