Hello ngoenyi.

You explanations on this concept are crystal clear and It is good that you have given a simple example in the starting of this post which will definitely help Steemians to understand about this concept more easily. Bollinger bands is great indicator and It can help a trader in technical analysis in various ways like in measuring the volatility of market or Sometimes, It's bands can also help in finding entry and exit points.

Great Post. Best of luck for the contest.