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Dec 17, 2020 at 13:12 comment added Let101 I was also wondering how does this problem change if, whenever $X\le k$, we decrease $t$ by $x+1$ (instead of by $1$), and the stopping condition is $t\le 0$? I guess in this case the "symmetry" of the problem could make it easier to solve.
Dec 17, 2020 at 13:10 comment added Let101 Thank you @NateEldredge for your comments. I see. Let $T$ be the random variable equal to total number of rolls (taking value $\tau\in[1,\infty]$), and let $D(r)~~ (:=D_{k,n}(r))$ be the total number of dollars won at round $r$. $D(r)<0$ means that we are loosing money at round $r$. Instead of asking for $\mathbb{E}[D(T)]$ as in the original problem version, would it be more meaningful to ask for $\mathbb{E}[\lim\sup_{r\to T}D(r)]$ and $\mathbb{E}[\lim\inf_{r\to T}D(r)]$?
Dec 17, 2020 at 4:35 comment added Nate Eldredge Wald does seem helpful because this is a random walk $S_m$ stopped at a stopping time $\tau$. However to apply it, we need to have $E[\tau] < \infty$ and as I note above, in most cases we do not even have $\tau < \infty$ a.s.
Dec 17, 2020 at 4:32 comment added Nate Eldredge If I'm not mistaken, whenever we take $k < n-1$, the counter $t$ has positive drift and there is a positive probability that the game never terminates. What do we mean by "total number of dollars won" in this case?
Dec 16, 2020 at 23:15 history edited Let101 CC BY-SA 4.0
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Dec 16, 2020 at 22:44 history edited Wlod AA CC BY-SA 4.0
Question named as such
Dec 16, 2020 at 22:40 comment added Let101 Is Wald's equation useful in this case?
Dec 16, 2020 at 22:40 history edited Let101 CC BY-SA 4.0
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Dec 16, 2020 at 22:28 comment added Wlod AA I feel that the q. about Wald should be moved to a comment.
Dec 16, 2020 at 21:42 history edited Let101 CC BY-SA 4.0
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Dec 16, 2020 at 21:42 comment added Let101 Yes @kodlu . The meaning basically is "When is convenient to play this game? (without loosing time)" Edited.
Dec 16, 2020 at 21:37 comment added kodlu Is "larger than" a strict inequality?
Dec 16, 2020 at 20:04 history edited Wlod AA CC BY-SA 4.0
a further improvement
Dec 16, 2020 at 19:59 history edited Wlod AA CC BY-SA 4.0
a clearer (more precise) formulation + fixing one or two typos.
Dec 16, 2020 at 19:30 history asked Let101 CC BY-SA 4.0