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Variance is the average of the squared differences from the mean. It is a play off of the word, "vary", to differ in size, degree, amount, or nature from something else of the same general class. The more often my mood changes and deviates from a display of being normal (no pun intended), the higher the variance. In finance, the term, "risk", is often synonymous with variance, but variance is the backbone of these discussions. The National Institute of Standards and Technology's (NIST) states that a measurement result is complete only when accompanied by a quantitative statement of its uncertainty.