What's the difference between taking a flat and closed bollinger band?

Unable to determine the opening direction.

Generally speaking, Brin's closing only shows that the market may change, but as for the changes there, it is uncertain.

In a few cases, it can even fluctuate within a narrow range for a long time.

Normative investment evaluation usually pursues a certain margin of safety. Brin's upper rail and lower rail can be regarded as such a safety margin, or a confidence interval.

However, due to the complexity of human social psychology (metabolism, profit-seeking, adaptability, plasticity, stress, variability and rhythm), this margin is often only theoretical or idealistic and has only reference significance.

The concept of statistical standard deviation is introduced in the calculation of Boolean orbit.

Calculation formula of daily bell index:

Intermediate trajectory =N-day moving average

Upper trajectory = middle trajectory+double standard deviation

Lower trajectory = middle trajectory-double standard deviation

It can be seen that the gradual narrowing of the distance between the upper and lower rails of Brin-that is, convergence-shows that the standard deviation is gradually narrowing, that is, the fluctuation tends to narrow.

In the performance of the stock price, it is a quiet period.

Similarly, due to the complexity of social psychology, this quiet period cannot be maintained for a long time and will inevitably change.

When the stock price breaks through the narrow upper or lower rail, the standard deviation of the stock price will gradually increase, that is, the volatility will increase. At the same time, it also means the expansion of the "margin of safety" and the violent fluctuations return to normal.

Long-term narrow fluctuation can occur anywhere except at the top: bottom, ascending relay or descending relay.