Oct 5, 2009

Bollinger Bands

Bollinger Bands
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Bollinger bands are formed by three lines. The middle line (ML) is a usual Moving Average.

ML = SUM [CLOSE, N]/N

The top line, TL, is the same as the middle line a certain number of standard deviations (D) higher than the ML.

TL = ML + (D*StdDev)

The bottom line (BL) is the middle line shifted down by the same number of standard deviations.

BL = ML — (D*StdDev)

Where:
N — is the number of periods used in calculation;
SMA — Simple Moving Average;
StdDev — means Standard Deviation.

StdDev = SQRT(SUM[(CLOSE — SMA(CLOSE, N))^2, N]/N)

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