Although John Bolinger recommends the value of the moving average based
on 20 cycles, this variable is optimized by changing it in different
markets, different instruments and at different times. In practice, a
maximum 20-day moving average is used.

Calculation formulas;شركات الفوركس الموثوقة

Medium Bollinger Band = 20 Daily Moving Average

Top Bollinger Band = Medium Bollinger Band + 2 Standard Deviation

Bottom Bollinger Band = Medium Bollinger Band - 2 Standard Deviation

According
to the characteristics of the market and the investment tool, the
standard deviation value is changed with the period based on the
Bollinger bands. For example; the veterans of the technical analysis say
it would be appropriate to revise the standard deviation of 2.5 to be
used if an average of 50 periods would be used instead of 20. If the
period is to be determined as 10 days, it is stated that the standard
deviation to be reduced to 1.5 is more healthy.خبراء توصيات الفوركس

John
Bollinger says that the prices that make up the basic rules of the
Bollinger Bands are ar high and low inger. It emphasizes that height and
low can be used to compare price and indicator movements in order to
make correct buying and selling decisions. John Bolinger points out
that: It is wrong to expect two indicators from the same category to
approve the situation to determine the price mobility, instead it is
better to confirm the Bollinger signals with Oscillators to produce more
successful results instead of volume indicators.