The Average True Range ("ATR") is a measure of
volatility. It was introduced by Welles Wilder in his book, New Concepts
in Technical Trading Systems, and has since been used as a component of
many indicators and trading systems.
Interpretation
Wilder has found that high ATR values often occur at
market bottoms following a "panic" sell-off. Low Average True Range
values are often found during extended sideways periods, such as those
found at tops and after consolidation periods.
The Average True Range can be interpreted using the
same techniques that are used with the other volatility indicators.
Refer to the discussion on Standard Deviation for additional information
on volatility interpretation.
Example
The following chart shows McDonald's and its Average
True Range.
This is a good example of high volatility as prices
bottom (points "A" and "A'") and low volatility as prices consolidate
prior to a breakout (points "B" and "B'").
Calculation
The True Range indicator is the greatest of the
following:
The distance from today's high to today's low.
The distance from yesterday's close to today's
high.
The distance from yesterday's close to today's
low.
The Average True Range is a moving average
(typically 14-days) of the True Ranges.