A trick used in Rademacher complexity related Theorem












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I am currently working on the proof of Theorem 3.1 in the book "Foundations of Machine Learning" (page 35, First edition), and there is a key trick used in the proof (equation 3.10 and 3.11):



$E_{S,S'}[supfrac{1}{m}sum(g(z'_i)-g(z_i))]=E_{mathrm{sigma},S,S'}[supfrac{1}{m}sumsigma(g(z'_i)-g(z_i))]$



It is also shown in the lecture pdf page 8 in this link:
https://cs.nyu.edu/~mohri/mls/lecture_3.pdf



This is possible because $z_i$ and $z'_i$ can be swapped. My question is, why can we swap $z_i$ and $z'_i$? In the book, it says this is possible because "we are taking the expectation over all possible $S$ and $S'$, it will not affect the overall expectation." Unfortunately, I don't understand the meaning or intuition of this part.



Thank you very much for reading the question and for your time!










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    1












    $begingroup$


    I am currently working on the proof of Theorem 3.1 in the book "Foundations of Machine Learning" (page 35, First edition), and there is a key trick used in the proof (equation 3.10 and 3.11):



    $E_{S,S'}[supfrac{1}{m}sum(g(z'_i)-g(z_i))]=E_{mathrm{sigma},S,S'}[supfrac{1}{m}sumsigma(g(z'_i)-g(z_i))]$



    It is also shown in the lecture pdf page 8 in this link:
    https://cs.nyu.edu/~mohri/mls/lecture_3.pdf



    This is possible because $z_i$ and $z'_i$ can be swapped. My question is, why can we swap $z_i$ and $z'_i$? In the book, it says this is possible because "we are taking the expectation over all possible $S$ and $S'$, it will not affect the overall expectation." Unfortunately, I don't understand the meaning or intuition of this part.



    Thank you very much for reading the question and for your time!










    share|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      I am currently working on the proof of Theorem 3.1 in the book "Foundations of Machine Learning" (page 35, First edition), and there is a key trick used in the proof (equation 3.10 and 3.11):



      $E_{S,S'}[supfrac{1}{m}sum(g(z'_i)-g(z_i))]=E_{mathrm{sigma},S,S'}[supfrac{1}{m}sumsigma(g(z'_i)-g(z_i))]$



      It is also shown in the lecture pdf page 8 in this link:
      https://cs.nyu.edu/~mohri/mls/lecture_3.pdf



      This is possible because $z_i$ and $z'_i$ can be swapped. My question is, why can we swap $z_i$ and $z'_i$? In the book, it says this is possible because "we are taking the expectation over all possible $S$ and $S'$, it will not affect the overall expectation." Unfortunately, I don't understand the meaning or intuition of this part.



      Thank you very much for reading the question and for your time!










      share|improve this question









      $endgroup$




      I am currently working on the proof of Theorem 3.1 in the book "Foundations of Machine Learning" (page 35, First edition), and there is a key trick used in the proof (equation 3.10 and 3.11):



      $E_{S,S'}[supfrac{1}{m}sum(g(z'_i)-g(z_i))]=E_{mathrm{sigma},S,S'}[supfrac{1}{m}sumsigma(g(z'_i)-g(z_i))]$



      It is also shown in the lecture pdf page 8 in this link:
      https://cs.nyu.edu/~mohri/mls/lecture_3.pdf



      This is possible because $z_i$ and $z'_i$ can be swapped. My question is, why can we swap $z_i$ and $z'_i$? In the book, it says this is possible because "we are taking the expectation over all possible $S$ and $S'$, it will not affect the overall expectation." Unfortunately, I don't understand the meaning or intuition of this part.



      Thank you very much for reading the question and for your time!







      machine-learning pac-learning






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