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Jun 26, 2023 at 19:46 comment added Iosif Pinelis @CuriousGuy : The martingale is $(E(\|S_k\|\,|\,X_1,\ldots,X_{k-1}))$, where $S_k:=X_1+\cdots+X_k$.
Jun 26, 2023 at 15:07 comment added CuriousGuy Thanks for the answer: what is the considered martingale then?
Jun 26, 2023 at 15:01 comment added Iosif Pinelis @CuriousGuy : The lower bound here is not on the probability to deviate from the mean -- notice the condition $u\le E\|X\|$.
Jun 26, 2023 at 14:49 comment added CuriousGuy How come the Azuma inequality becomes an anti-concentration one? The bound should be a concentration bound around the mean, not a lower bound on the probability to deviate from the mean. Am I wrong?
Feb 21, 2020 at 9:23 vote accept ABIM
Feb 20, 2020 at 0:30 comment added Iosif Pinelis @oferzeitouni : Thank you for your comment. This is now corrected.
Feb 20, 2020 at 0:19 history edited Iosif Pinelis CC BY-SA 4.0
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Feb 19, 2020 at 20:07 comment added ofer zeitouni Hmm. The Hoeffding-Azuma inequality you quote is not the one in the reference, and is actually wrong as the example $n=1$ and $u=E|X|$ shows. I believe there is a typo also in the reference you give (Bartlett's notes) - it should be an upper bound, not a lower bound, as the example t=0 (and the proof given there) show.
Feb 19, 2020 at 19:47 history edited Iosif Pinelis CC BY-SA 4.0
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Feb 19, 2020 at 18:11 history edited Iosif Pinelis CC BY-SA 4.0
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Feb 19, 2020 at 18:03 history answered Iosif Pinelis CC BY-SA 4.0