Martingale Definition: A sequence of random variables Xo,X1,...is a martingale if for all i>0, E[Xi KXo,...,Xi=Xi-1 What does this mean?E[Xi | X0,...,Xi⇥1] = Xi⇥1 Definition: A sequence of random variables X0,X1,... is a martingale if for all i > 0, Martingale What does this mean?