Standard deviation and variance are two statistical measures for dispersion. They can be used to determine how variable or volatile a series of data is. Your best friend, Barry Markowitz, has argued that risk can be measured using either standard deviation or variance. That is, if you want to know how risky a share or a currency is, for example, you would measure the standard deviation or variance of the share returns or the currency price over time. Is Barry correct? If so, why?

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