# Bollinger Oscillator (BOS)

## Bollinger Oscillator Overview

The bollinger oscillator is an economic indicators which measures the standard deviation of the price from a simple moving average. It can be calculated using a 20-day simple moving average but is usually calculated using a 9-day moving average.

The bollinger oscillator is pictured below: Just below the volume and above the MACD is the Bollinger Oscillator (BOS) indicator.

A signal to buy a share would be when the Bollinger Oscillator (BOS) is below -2.  A signal to sell a share would be when the Bollinger Oscillator (BOS) isabove 2. Meaning that the ruling share price is 2 standard deviations below and above  the moving average respectively. You can use the bands in the same way buying when the price moves below the lower band and selling when the share moves above the upper band.

## BOS Calculation

To Calculate the Bollinger Oscillator (BOS):

1. Find the 9-day moving average average (n1 + n2 ... + n9)/9
2. Find the standard deviation of the 9-days
3. Subtract 9-day Moving average from the current ruling price
4. Take the answer devide by the standard deviation
5. Answer is the BOS (Bollinger Oscillator)

## Bands Calculation

To Calculate the Bollinger Bands:

1. Find the 20-day moving average average (n1 + n2 ... + n20)/20
2. Find the standard deviation of the 20-days
3. Upper Band = 20-day Moving Average + (2 x standard deviation of the 20-days)
4. Lower Band = 20-day Moving Average - (2 x standard deviation of the 20-days)