Please note that the content of this book primarily consists of articles
available from Wikipedia or other free sources online. Trembling hand
perfect equilibrium is a refinement of Nash Equilibrium due to Reinhard
Selten. A trembling hand perfect equilibrium is an equilibrium that
takes the possibility of off-the-equilibrium play into account by
assuming that the players, through a "slip of the hand" or tremble, may
choose unintended strategies, albeit with negligible probability. An
extensive-form trembling hand perfect equilibrium is also a sequential
equilibrium. A normal-form trembling hand perfect equilibrium of an
extensive form game may be sequential but is not necessarily so. In
fact, a normal-form trembling hand perfect equilibrium does not even
have to be subgame perfect.The notions of normal-form and extensive-form
trembling hand perfect equilibria are incomparable, i.e., an equilibrium
of an extensive-form game may be normal-form trembling hand perfect but
not extensive-form trembling hand perfect and vice versa.
