Bollinger Bands consist of a N-period Moving Average (MA), an Upper Band at K times an N-period standard deviation above the Moving Average (MA + Kσ), and a Lower Band at K times an N-period standard deviation below the Moving Average (MA − Kσ). This version does not use ...
from https://tradingrobots.net/bollinger-bands-ema-deviation-indicator-for-metatrader-5/