Upper bound probability of variable that decreases at every step











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I'm having a hard time wrapping my mind around this small probability problem.



We start with a variable $X$, that has some fixed integer value in $[d,n]$. At each step, there is a $frac{X}{n}$ chance that we decrease the value of $X$ by 1. We repeat this $m$ times.



What is an upper bound on the probability that the value of $X$ is $geq d$ at the end of this?










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    up vote
    0
    down vote

    favorite












    I'm having a hard time wrapping my mind around this small probability problem.



    We start with a variable $X$, that has some fixed integer value in $[d,n]$. At each step, there is a $frac{X}{n}$ chance that we decrease the value of $X$ by 1. We repeat this $m$ times.



    What is an upper bound on the probability that the value of $X$ is $geq d$ at the end of this?










    share|cite|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I'm having a hard time wrapping my mind around this small probability problem.



      We start with a variable $X$, that has some fixed integer value in $[d,n]$. At each step, there is a $frac{X}{n}$ chance that we decrease the value of $X$ by 1. We repeat this $m$ times.



      What is an upper bound on the probability that the value of $X$ is $geq d$ at the end of this?










      share|cite|improve this question













      I'm having a hard time wrapping my mind around this small probability problem.



      We start with a variable $X$, that has some fixed integer value in $[d,n]$. At each step, there is a $frac{X}{n}$ chance that we decrease the value of $X$ by 1. We repeat this $m$ times.



      What is an upper bound on the probability that the value of $X$ is $geq d$ at the end of this?







      probability






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      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Nov 15 at 3:07









      Claire Chen

      133




      133



























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