Boll index is to calculate the "standard deviation" of the stock price, and then find the "trust interval" of the stock price. The indicator draws three lines on the graph, in which the upper and lower lines can be regarded as the pressure line and the support line of the stock price respectively, and there is an average line of the stock price between the two lines.

Attachment: Matters needing attention in the use of bollinger bands

1, the bollinger band parameter setting shall not be less than 6, and the static dry heave value is usually10; Dynamic stem length is generally set to 20.

2. When using the bollinger Band, pay attention to whether it is in the normal area or the abnormal area. In the abnormal area, we can't simply follow the principle of breaking the upper limit and buying the lower limit.

3. It is easy to catch bull stocks by narrowing the opening at a low level, but at a high level or once it is reduced, the stock price will break down and there will often be more room for decline.

4. Bollinger Bands can be used in conjunction with other indicators, and the effect will be better, such as volume and KDJ indicators.