Option Volatility  Volatility is a statistical measurement of
the degree of fluctuation of a market or security. Volatility is
computed as the annualized standard deviation of daily
percentage price changes of the security and is expressed as a
percentage.  Historical Volatility (HV)  Historical volatility
measures how volatile the security has been in the past. To
compute historical volatility, you must first define a look-back
period. Twenty day periods are commonly used as it approximates
the number of trading days in a month.  Implied Volatility (IV)
Implied volatility is the volatility as implied by the market
price of the security's options. The implied volatility is
calculated using an option pricing model, such as the Black
Scholes model, in which a mathematical relationship between the
volatility of the underlying security and the price of its
options has been established.  In other words, implied
volatility is the market's opinion of the volatility of the
option's underlying security and is determi