Disclosure: All opinions expressed and data provided are subject to change without notice. Some of these opinions may not be appropriate to every investor.

Standard deviation is a measure of the dispersion of a set of data from its mean. The more spread apart the data, the higher the deviation. Standard deviation is also known as historical volatility.

The S&P 500 Stock Index is a widely recognized capitalization-weighted index of 500 common stock prices in U.S. companies.

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