Asymptotic Statistics: Convergence in distribution to a tight CDF implies convergence in probability to a...












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I'm taking a course in asymptotic statistics, and I'm having trouble with how to start proving the following statement. I learn best from examples, rather than just reading the theorems, however I can't find an example that seems similar. Any and all help is appreciated!



$$
left.
begin{matrix}
k_n left( Y_n -c right) xrightarrow{D} H \
k_n to infty
end{matrix}
right} implies Y_n xrightarrow{P} c
$$

There is the additional hint: You may assume without loss of generality that $H$ is the cumulative distribution function of a random variable $V$ which is tight meaning that, given any $epsilon > 0$, there exists a finite number $M$ such that $P(|V | leq M) geq 1 − epsilon/2$.





When I look at this, I instinctively think of the Central Limit Theorem with $k_n = sqrt{n}$, $Y_n = bar{X}_n$, $c=mu$ and $H$ the CDF some normally distributed r.v. $V$. I understand the concept of tightness which implies that none of the PMF escapes to infinity, so that makes me think I'm incorrect in assuming $V$ is normal.










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    $begingroup$


    I'm taking a course in asymptotic statistics, and I'm having trouble with how to start proving the following statement. I learn best from examples, rather than just reading the theorems, however I can't find an example that seems similar. Any and all help is appreciated!



    $$
    left.
    begin{matrix}
    k_n left( Y_n -c right) xrightarrow{D} H \
    k_n to infty
    end{matrix}
    right} implies Y_n xrightarrow{P} c
    $$

    There is the additional hint: You may assume without loss of generality that $H$ is the cumulative distribution function of a random variable $V$ which is tight meaning that, given any $epsilon > 0$, there exists a finite number $M$ such that $P(|V | leq M) geq 1 − epsilon/2$.





    When I look at this, I instinctively think of the Central Limit Theorem with $k_n = sqrt{n}$, $Y_n = bar{X}_n$, $c=mu$ and $H$ the CDF some normally distributed r.v. $V$. I understand the concept of tightness which implies that none of the PMF escapes to infinity, so that makes me think I'm incorrect in assuming $V$ is normal.










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      I'm taking a course in asymptotic statistics, and I'm having trouble with how to start proving the following statement. I learn best from examples, rather than just reading the theorems, however I can't find an example that seems similar. Any and all help is appreciated!



      $$
      left.
      begin{matrix}
      k_n left( Y_n -c right) xrightarrow{D} H \
      k_n to infty
      end{matrix}
      right} implies Y_n xrightarrow{P} c
      $$

      There is the additional hint: You may assume without loss of generality that $H$ is the cumulative distribution function of a random variable $V$ which is tight meaning that, given any $epsilon > 0$, there exists a finite number $M$ such that $P(|V | leq M) geq 1 − epsilon/2$.





      When I look at this, I instinctively think of the Central Limit Theorem with $k_n = sqrt{n}$, $Y_n = bar{X}_n$, $c=mu$ and $H$ the CDF some normally distributed r.v. $V$. I understand the concept of tightness which implies that none of the PMF escapes to infinity, so that makes me think I'm incorrect in assuming $V$ is normal.










      share|cite|improve this question









      $endgroup$




      I'm taking a course in asymptotic statistics, and I'm having trouble with how to start proving the following statement. I learn best from examples, rather than just reading the theorems, however I can't find an example that seems similar. Any and all help is appreciated!



      $$
      left.
      begin{matrix}
      k_n left( Y_n -c right) xrightarrow{D} H \
      k_n to infty
      end{matrix}
      right} implies Y_n xrightarrow{P} c
      $$

      There is the additional hint: You may assume without loss of generality that $H$ is the cumulative distribution function of a random variable $V$ which is tight meaning that, given any $epsilon > 0$, there exists a finite number $M$ such that $P(|V | leq M) geq 1 − epsilon/2$.





      When I look at this, I instinctively think of the Central Limit Theorem with $k_n = sqrt{n}$, $Y_n = bar{X}_n$, $c=mu$ and $H$ the CDF some normally distributed r.v. $V$. I understand the concept of tightness which implies that none of the PMF escapes to infinity, so that makes me think I'm incorrect in assuming $V$ is normal.







      statistics asymptotics weak-convergence






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      asked Jan 24 at 11:57









      StephanieStephanie

      83




      83






















          1 Answer
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          $begingroup$

          Let $epsilon >0$. Let $M$ be as given in the hint. Without loss of generality we may assume that $H$ is continuous at $pm M$. If $k_n >frac M {epsilon}$ then $P{|Y_n-c| >epsilon} =P{|k_n(Y_n-c)| >k_n epsilon}leq P{|k_n(Y_n-c)| >M} to P{|V| >M} <epsilon /2$.






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          $endgroup$













          • $begingroup$
            Thanks for your help Kavi! The $to$ implication, does that stem from: as $epsilon$ is arbitrary and $M$ is fixed and finite, $epsilonto 0$ as $k_n to infty$? Or is it an implication of the convergence in distribution? Usually that requires some type of $n$ involved in the terms, is that right? Should $epsilon$ be defined as some type of inverse on $n$ to achieve this?
            $endgroup$
            – Stephanie
            Jan 24 at 13:28













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          $begingroup$

          Let $epsilon >0$. Let $M$ be as given in the hint. Without loss of generality we may assume that $H$ is continuous at $pm M$. If $k_n >frac M {epsilon}$ then $P{|Y_n-c| >epsilon} =P{|k_n(Y_n-c)| >k_n epsilon}leq P{|k_n(Y_n-c)| >M} to P{|V| >M} <epsilon /2$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks for your help Kavi! The $to$ implication, does that stem from: as $epsilon$ is arbitrary and $M$ is fixed and finite, $epsilonto 0$ as $k_n to infty$? Or is it an implication of the convergence in distribution? Usually that requires some type of $n$ involved in the terms, is that right? Should $epsilon$ be defined as some type of inverse on $n$ to achieve this?
            $endgroup$
            – Stephanie
            Jan 24 at 13:28


















          1












          $begingroup$

          Let $epsilon >0$. Let $M$ be as given in the hint. Without loss of generality we may assume that $H$ is continuous at $pm M$. If $k_n >frac M {epsilon}$ then $P{|Y_n-c| >epsilon} =P{|k_n(Y_n-c)| >k_n epsilon}leq P{|k_n(Y_n-c)| >M} to P{|V| >M} <epsilon /2$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks for your help Kavi! The $to$ implication, does that stem from: as $epsilon$ is arbitrary and $M$ is fixed and finite, $epsilonto 0$ as $k_n to infty$? Or is it an implication of the convergence in distribution? Usually that requires some type of $n$ involved in the terms, is that right? Should $epsilon$ be defined as some type of inverse on $n$ to achieve this?
            $endgroup$
            – Stephanie
            Jan 24 at 13:28
















          1












          1








          1





          $begingroup$

          Let $epsilon >0$. Let $M$ be as given in the hint. Without loss of generality we may assume that $H$ is continuous at $pm M$. If $k_n >frac M {epsilon}$ then $P{|Y_n-c| >epsilon} =P{|k_n(Y_n-c)| >k_n epsilon}leq P{|k_n(Y_n-c)| >M} to P{|V| >M} <epsilon /2$.






          share|cite|improve this answer









          $endgroup$



          Let $epsilon >0$. Let $M$ be as given in the hint. Without loss of generality we may assume that $H$ is continuous at $pm M$. If $k_n >frac M {epsilon}$ then $P{|Y_n-c| >epsilon} =P{|k_n(Y_n-c)| >k_n epsilon}leq P{|k_n(Y_n-c)| >M} to P{|V| >M} <epsilon /2$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 24 at 12:11









          Kavi Rama MurthyKavi Rama Murthy

          67.6k53067




          67.6k53067












          • $begingroup$
            Thanks for your help Kavi! The $to$ implication, does that stem from: as $epsilon$ is arbitrary and $M$ is fixed and finite, $epsilonto 0$ as $k_n to infty$? Or is it an implication of the convergence in distribution? Usually that requires some type of $n$ involved in the terms, is that right? Should $epsilon$ be defined as some type of inverse on $n$ to achieve this?
            $endgroup$
            – Stephanie
            Jan 24 at 13:28




















          • $begingroup$
            Thanks for your help Kavi! The $to$ implication, does that stem from: as $epsilon$ is arbitrary and $M$ is fixed and finite, $epsilonto 0$ as $k_n to infty$? Or is it an implication of the convergence in distribution? Usually that requires some type of $n$ involved in the terms, is that right? Should $epsilon$ be defined as some type of inverse on $n$ to achieve this?
            $endgroup$
            – Stephanie
            Jan 24 at 13:28


















          $begingroup$
          Thanks for your help Kavi! The $to$ implication, does that stem from: as $epsilon$ is arbitrary and $M$ is fixed and finite, $epsilonto 0$ as $k_n to infty$? Or is it an implication of the convergence in distribution? Usually that requires some type of $n$ involved in the terms, is that right? Should $epsilon$ be defined as some type of inverse on $n$ to achieve this?
          $endgroup$
          – Stephanie
          Jan 24 at 13:28






          $begingroup$
          Thanks for your help Kavi! The $to$ implication, does that stem from: as $epsilon$ is arbitrary and $M$ is fixed and finite, $epsilonto 0$ as $k_n to infty$? Or is it an implication of the convergence in distribution? Usually that requires some type of $n$ involved in the terms, is that right? Should $epsilon$ be defined as some type of inverse on $n$ to achieve this?
          $endgroup$
          – Stephanie
          Jan 24 at 13:28




















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