Problem bank

Problem 297 of 333HardStochastic ProcessesP297

Up ten before flat again

  1. Your P&L starts at 0 and each trade moves it up or down by $1 with probability 1/21/2 each, independently.

    (a) What is the probability that the P&L reaches a profit of $10 before it first returns to 0?

    (b) Count the trades after which the P&L equals exactly $10, up to the moment it first returns to 0. What is the expected count?