Hi everyone. I was going through a proof of Wald's equation, where it was claimed that if {S_n} is a sequence defined as S_n = \sum_1^{n} Y_i where the Y_i are iid with finite mean \mu, then Z_n = S_n - n \mu is a martingale.(adsbygoogle = window.adsbygoogle || []).push({});

But I don't see why... at all!

Help!

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# Simple martingale question.

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