Commodity Channel Index is calculated by determining the difference between
the mean price of a security and the average of the means over the period chosen.
This difference is compared to the average difference over the time period. The
result is multiplied by a constant to make sure that most values fall within the
standard range of +/- 100.

It is recommended to look for divergences between the indicator and price. Also,
look for extreme readings above 100 and below -100 to indicate overbought and
oversold levels.