The Black-Scholes option pricing methodology requires that the model for the price of the underlying asset be completely specified. Often the underlying price is taken to be a geometric Brownian motion with a constant, known volatility. In practice one does not know precise values of parameters...

The Black-Scholes theory of option pricing requires a perfectly specified model for the underlying price. Frequently this is taken to be a geometric Brownian motion with a constant, known volatility. In practice, parameters such as the volatility are not known precisely, but are simply estimates...