#volatility

Beta is the slope of a regression of a stock's returns against the market's. That's the whole definition. It says nothing about how risky the stock is, and once you put R-squared next to it, a 0.5-beta stock can be more volatile than a 1.8-beta one.

Bollinger Bands are a 20-day moving average with two lines drawn two standard deviations away. The math is high school stats. The hard part is knowing what to do with them.

Volatility isn’t the same thing as risk. It isn’t the same thing as direction. And the most-quoted volatility number on TV measures something almost nobody understands.