Upperbounding the expected value of an L2-norm difference












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I am trying to find an upperbound for $$E_Ileft[sum_{k=I}^n a_k^2 - sum_{k=I}^n b_k^2right],$$ where the expectation is taken over the random variable $I$. The tuples $a$ and $b$ are real and $I$ may take values on ${1,...,n}$.



I checked Jensen's inequalites but without success. Any help would be appreciated.










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  • What is the relation between $a_k, b_k$ and $I$?
    – herb steinberg
    Nov 26 '18 at 22:50










  • Assuming you seek a bound on the expectation of a random length sum of fixed real numbers, clearly $||a||_2^2=sum_{k=1}^n a_k^2$ is an upper bound.
    – Macavity
    Nov 27 '18 at 1:29


















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I am trying to find an upperbound for $$E_Ileft[sum_{k=I}^n a_k^2 - sum_{k=I}^n b_k^2right],$$ where the expectation is taken over the random variable $I$. The tuples $a$ and $b$ are real and $I$ may take values on ${1,...,n}$.



I checked Jensen's inequalites but without success. Any help would be appreciated.










share|cite|improve this question






















  • What is the relation between $a_k, b_k$ and $I$?
    – herb steinberg
    Nov 26 '18 at 22:50










  • Assuming you seek a bound on the expectation of a random length sum of fixed real numbers, clearly $||a||_2^2=sum_{k=1}^n a_k^2$ is an upper bound.
    – Macavity
    Nov 27 '18 at 1:29
















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0







I am trying to find an upperbound for $$E_Ileft[sum_{k=I}^n a_k^2 - sum_{k=I}^n b_k^2right],$$ where the expectation is taken over the random variable $I$. The tuples $a$ and $b$ are real and $I$ may take values on ${1,...,n}$.



I checked Jensen's inequalites but without success. Any help would be appreciated.










share|cite|improve this question













I am trying to find an upperbound for $$E_Ileft[sum_{k=I}^n a_k^2 - sum_{k=I}^n b_k^2right],$$ where the expectation is taken over the random variable $I$. The tuples $a$ and $b$ are real and $I$ may take values on ${1,...,n}$.



I checked Jensen's inequalites but without success. Any help would be appreciated.







probability inequality norm jensen-inequality






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asked Nov 26 '18 at 19:04









Embid

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  • What is the relation between $a_k, b_k$ and $I$?
    – herb steinberg
    Nov 26 '18 at 22:50










  • Assuming you seek a bound on the expectation of a random length sum of fixed real numbers, clearly $||a||_2^2=sum_{k=1}^n a_k^2$ is an upper bound.
    – Macavity
    Nov 27 '18 at 1:29




















  • What is the relation between $a_k, b_k$ and $I$?
    – herb steinberg
    Nov 26 '18 at 22:50










  • Assuming you seek a bound on the expectation of a random length sum of fixed real numbers, clearly $||a||_2^2=sum_{k=1}^n a_k^2$ is an upper bound.
    – Macavity
    Nov 27 '18 at 1:29


















What is the relation between $a_k, b_k$ and $I$?
– herb steinberg
Nov 26 '18 at 22:50




What is the relation between $a_k, b_k$ and $I$?
– herb steinberg
Nov 26 '18 at 22:50












Assuming you seek a bound on the expectation of a random length sum of fixed real numbers, clearly $||a||_2^2=sum_{k=1}^n a_k^2$ is an upper bound.
– Macavity
Nov 27 '18 at 1:29






Assuming you seek a bound on the expectation of a random length sum of fixed real numbers, clearly $||a||_2^2=sum_{k=1}^n a_k^2$ is an upper bound.
– Macavity
Nov 27 '18 at 1:29

















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