Let $X_n$ be a uniform distribution on $(-1,1)$. Let$ Y_n$ ~ Cauchy(0,1). Everything independent.












0












$begingroup$


Let $X_n$ be a uniform distribution on $(-1,1)$. Let$ Y_n$ ~ Cauchy(0,1). Everything independent.



Let $Z_n$ = $X_n$ + $Y_n$



I want to study the law convergence of the sample mean of $Z_n$. That is:



$$ overline{Z_n} = frac{sum X_i + sum Y_i}{n} $$



So, first of all there is an hint: I cannot use the Law of large numbers. Why is that?



Anyway, I am really out of tools to attack this problem. Does someone have a hint?



EDIT: Managed to prove that sample mean of Cauchy is still Cauchy! Still not sure about the solution.










share|cite|improve this question









$endgroup$

















    0












    $begingroup$


    Let $X_n$ be a uniform distribution on $(-1,1)$. Let$ Y_n$ ~ Cauchy(0,1). Everything independent.



    Let $Z_n$ = $X_n$ + $Y_n$



    I want to study the law convergence of the sample mean of $Z_n$. That is:



    $$ overline{Z_n} = frac{sum X_i + sum Y_i}{n} $$



    So, first of all there is an hint: I cannot use the Law of large numbers. Why is that?



    Anyway, I am really out of tools to attack this problem. Does someone have a hint?



    EDIT: Managed to prove that sample mean of Cauchy is still Cauchy! Still not sure about the solution.










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      Let $X_n$ be a uniform distribution on $(-1,1)$. Let$ Y_n$ ~ Cauchy(0,1). Everything independent.



      Let $Z_n$ = $X_n$ + $Y_n$



      I want to study the law convergence of the sample mean of $Z_n$. That is:



      $$ overline{Z_n} = frac{sum X_i + sum Y_i}{n} $$



      So, first of all there is an hint: I cannot use the Law of large numbers. Why is that?



      Anyway, I am really out of tools to attack this problem. Does someone have a hint?



      EDIT: Managed to prove that sample mean of Cauchy is still Cauchy! Still not sure about the solution.










      share|cite|improve this question









      $endgroup$




      Let $X_n$ be a uniform distribution on $(-1,1)$. Let$ Y_n$ ~ Cauchy(0,1). Everything independent.



      Let $Z_n$ = $X_n$ + $Y_n$



      I want to study the law convergence of the sample mean of $Z_n$. That is:



      $$ overline{Z_n} = frac{sum X_i + sum Y_i}{n} $$



      So, first of all there is an hint: I cannot use the Law of large numbers. Why is that?



      Anyway, I am really out of tools to attack this problem. Does someone have a hint?



      EDIT: Managed to prove that sample mean of Cauchy is still Cauchy! Still not sure about the solution.







      probability weak-convergence law-of-large-numbers






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      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 15 at 16:59









      qcc101qcc101

      629213




      629213






















          1 Answer
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          $begingroup$

          Hint: what does $sum X_i / n$ converge to? As you note, the sum $sum Y_i / n$ is equal in distribution to a standard Cauchy.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            I guess it converges to $0$? Not sure how to prove it though. Followup question: can I say something about $Z_n$ belonging to some $L^p?$
            $endgroup$
            – qcc101
            Jan 15 at 17:08












          • $begingroup$
            @qcc101, yes it converges to $0$. The $X_n$'s are very nice random variables (they're bounded, even), so what theorem can we use to show that their average converges to 0? You can't say anything about the $overline{Z}_n$'s being in a nice $L^p$ space since Cauchy random variables aren't.
            $endgroup$
            – Marcus M
            Jan 15 at 17:10










          • $begingroup$
            I think I would try to use law of large numbers and then Slutsky to conclude, is that right?
            $endgroup$
            – qcc101
            Jan 15 at 17:15










          • $begingroup$
            @qcc101, yep that'll do it!
            $endgroup$
            – Marcus M
            Jan 15 at 17:17










          • $begingroup$
            Nice, thank you for the follow-ups it was exactly how I wanted to solve it.
            $endgroup$
            – qcc101
            Jan 15 at 17:19












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          1 Answer
          1






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          active

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          1












          $begingroup$

          Hint: what does $sum X_i / n$ converge to? As you note, the sum $sum Y_i / n$ is equal in distribution to a standard Cauchy.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            I guess it converges to $0$? Not sure how to prove it though. Followup question: can I say something about $Z_n$ belonging to some $L^p?$
            $endgroup$
            – qcc101
            Jan 15 at 17:08












          • $begingroup$
            @qcc101, yes it converges to $0$. The $X_n$'s are very nice random variables (they're bounded, even), so what theorem can we use to show that their average converges to 0? You can't say anything about the $overline{Z}_n$'s being in a nice $L^p$ space since Cauchy random variables aren't.
            $endgroup$
            – Marcus M
            Jan 15 at 17:10










          • $begingroup$
            I think I would try to use law of large numbers and then Slutsky to conclude, is that right?
            $endgroup$
            – qcc101
            Jan 15 at 17:15










          • $begingroup$
            @qcc101, yep that'll do it!
            $endgroup$
            – Marcus M
            Jan 15 at 17:17










          • $begingroup$
            Nice, thank you for the follow-ups it was exactly how I wanted to solve it.
            $endgroup$
            – qcc101
            Jan 15 at 17:19
















          1












          $begingroup$

          Hint: what does $sum X_i / n$ converge to? As you note, the sum $sum Y_i / n$ is equal in distribution to a standard Cauchy.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            I guess it converges to $0$? Not sure how to prove it though. Followup question: can I say something about $Z_n$ belonging to some $L^p?$
            $endgroup$
            – qcc101
            Jan 15 at 17:08












          • $begingroup$
            @qcc101, yes it converges to $0$. The $X_n$'s are very nice random variables (they're bounded, even), so what theorem can we use to show that their average converges to 0? You can't say anything about the $overline{Z}_n$'s being in a nice $L^p$ space since Cauchy random variables aren't.
            $endgroup$
            – Marcus M
            Jan 15 at 17:10










          • $begingroup$
            I think I would try to use law of large numbers and then Slutsky to conclude, is that right?
            $endgroup$
            – qcc101
            Jan 15 at 17:15










          • $begingroup$
            @qcc101, yep that'll do it!
            $endgroup$
            – Marcus M
            Jan 15 at 17:17










          • $begingroup$
            Nice, thank you for the follow-ups it was exactly how I wanted to solve it.
            $endgroup$
            – qcc101
            Jan 15 at 17:19














          1












          1








          1





          $begingroup$

          Hint: what does $sum X_i / n$ converge to? As you note, the sum $sum Y_i / n$ is equal in distribution to a standard Cauchy.






          share|cite|improve this answer









          $endgroup$



          Hint: what does $sum X_i / n$ converge to? As you note, the sum $sum Y_i / n$ is equal in distribution to a standard Cauchy.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 15 at 17:07









          Marcus MMarcus M

          8,84911047




          8,84911047












          • $begingroup$
            I guess it converges to $0$? Not sure how to prove it though. Followup question: can I say something about $Z_n$ belonging to some $L^p?$
            $endgroup$
            – qcc101
            Jan 15 at 17:08












          • $begingroup$
            @qcc101, yes it converges to $0$. The $X_n$'s are very nice random variables (they're bounded, even), so what theorem can we use to show that their average converges to 0? You can't say anything about the $overline{Z}_n$'s being in a nice $L^p$ space since Cauchy random variables aren't.
            $endgroup$
            – Marcus M
            Jan 15 at 17:10










          • $begingroup$
            I think I would try to use law of large numbers and then Slutsky to conclude, is that right?
            $endgroup$
            – qcc101
            Jan 15 at 17:15










          • $begingroup$
            @qcc101, yep that'll do it!
            $endgroup$
            – Marcus M
            Jan 15 at 17:17










          • $begingroup$
            Nice, thank you for the follow-ups it was exactly how I wanted to solve it.
            $endgroup$
            – qcc101
            Jan 15 at 17:19


















          • $begingroup$
            I guess it converges to $0$? Not sure how to prove it though. Followup question: can I say something about $Z_n$ belonging to some $L^p?$
            $endgroup$
            – qcc101
            Jan 15 at 17:08












          • $begingroup$
            @qcc101, yes it converges to $0$. The $X_n$'s are very nice random variables (they're bounded, even), so what theorem can we use to show that their average converges to 0? You can't say anything about the $overline{Z}_n$'s being in a nice $L^p$ space since Cauchy random variables aren't.
            $endgroup$
            – Marcus M
            Jan 15 at 17:10










          • $begingroup$
            I think I would try to use law of large numbers and then Slutsky to conclude, is that right?
            $endgroup$
            – qcc101
            Jan 15 at 17:15










          • $begingroup$
            @qcc101, yep that'll do it!
            $endgroup$
            – Marcus M
            Jan 15 at 17:17










          • $begingroup$
            Nice, thank you for the follow-ups it was exactly how I wanted to solve it.
            $endgroup$
            – qcc101
            Jan 15 at 17:19
















          $begingroup$
          I guess it converges to $0$? Not sure how to prove it though. Followup question: can I say something about $Z_n$ belonging to some $L^p?$
          $endgroup$
          – qcc101
          Jan 15 at 17:08






          $begingroup$
          I guess it converges to $0$? Not sure how to prove it though. Followup question: can I say something about $Z_n$ belonging to some $L^p?$
          $endgroup$
          – qcc101
          Jan 15 at 17:08














          $begingroup$
          @qcc101, yes it converges to $0$. The $X_n$'s are very nice random variables (they're bounded, even), so what theorem can we use to show that their average converges to 0? You can't say anything about the $overline{Z}_n$'s being in a nice $L^p$ space since Cauchy random variables aren't.
          $endgroup$
          – Marcus M
          Jan 15 at 17:10




          $begingroup$
          @qcc101, yes it converges to $0$. The $X_n$'s are very nice random variables (they're bounded, even), so what theorem can we use to show that their average converges to 0? You can't say anything about the $overline{Z}_n$'s being in a nice $L^p$ space since Cauchy random variables aren't.
          $endgroup$
          – Marcus M
          Jan 15 at 17:10












          $begingroup$
          I think I would try to use law of large numbers and then Slutsky to conclude, is that right?
          $endgroup$
          – qcc101
          Jan 15 at 17:15




          $begingroup$
          I think I would try to use law of large numbers and then Slutsky to conclude, is that right?
          $endgroup$
          – qcc101
          Jan 15 at 17:15












          $begingroup$
          @qcc101, yep that'll do it!
          $endgroup$
          – Marcus M
          Jan 15 at 17:17




          $begingroup$
          @qcc101, yep that'll do it!
          $endgroup$
          – Marcus M
          Jan 15 at 17:17












          $begingroup$
          Nice, thank you for the follow-ups it was exactly how I wanted to solve it.
          $endgroup$
          – qcc101
          Jan 15 at 17:19




          $begingroup$
          Nice, thank you for the follow-ups it was exactly how I wanted to solve it.
          $endgroup$
          – qcc101
          Jan 15 at 17:19


















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