English: varance

What is the geometric meaning of variance of random variables? What is the physical meaning?

The second-order center distance, also known as variance, tells us the fluctuation of a random variable near its mean. The greater the variance, the greater the fluctuation.

Variance is also equivalent to the moment of inertia with the center of gravity as the rotation axis in mechanical motion. (moment of inertia. )

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A is constant? Then E(a)=a, and

var(a) = E{a-E(a)}？ = E{a-a}？ = 0