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Re: How to find the mean and variance of 1/X?

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  • mahe_iima
    ... new ... Hi If X 0, ie. X assumes only positive values and E(X) and E(1/X)exist then E(1/X) = 1/E(X)because 1/X is a convex function.
    Message 1 of 5 , Nov 20, 2006
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      --- In probability@yahoogroups.com, "zak_hi79" <zak_hi79@...> wrote:
      >
      > --- In probability@yahoogroups.com, wilson wu <wilsonwxwu@> wrote:
      > >Dear Friend,
      > I suggist to assume that y=1/x and make a transformation to this
      new
      > r.v (y) and find f(y) then you can find the mean and variance.
      >
      > I will try to find it but it will take some times
      > All my best
      > ZAKaRIA
      > > Excuse me.
      > >
      > > I have worked this question several days.
      > >
      > > Assume X follow a NORMAL distribution with mean A and variance B,
      > how to find the the mean and variance of 1/X?
      > >
      > > Thank you very much.

      Hi
      If X >0, ie. X assumes only positive values and E(X) and E(1/X)exist
      then E(1/X)>= 1/E(X)because 1/X is a convex function.


      > >
      > > Best wishes,
      > >
      > > Wilson
      > >
      > >
      > > Wilson Weixing Wu
      > >
      > > School of Finance and Banking,
      > > University of International Business and Economics,
      > > Beijing 100029, China
      > >
      > >
      > > Tel. 0086-10-64495048 (office)
      > >
      > > Fax. 0086-10-64495059
      > >
      > > Email: wxwu@
      > >
      > > Email: Wilsonwxwu@
      > >
      > > ---------------------------------
      > > ÇÀ×¢ÑÅ»¢Ãâ·ÑÓÊÏä-3.5GÈÝÁ¿£¬20M¸½¼þ£¡
      > >
      > > [Non-text portions of this message have been removed]
      > >
      >
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