I know that $var(X)=E[(X-E(X))^2]$ .
However, I am confused because it seems to me that this definition is recursive in that the expected value of the square is itself a function of an expected value. Can anyone please clarify this?
2026-03-27 22:59:29.1774652369
Understanding variance formula
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Variance measures spread. The formula says that variance is the averaged squared distance from the mean. For small examples, I have my students do the following:
Take a data set and find its mean. Then, find how far away, plus or minus, each observation is from the mean (i.e., the deviations). Now square those distances and find that average.