The Empirical Rule is just a really basic rule of thumb for estimating the width of a bell curve based on standard deviation, or estimating standard deviation based on a bell curve (divide the width of the bell by 4).

Chebyshev’s Theorem

This is basically just like the Empirical Rule except that it works for any distribution, not just bell-shaped normal-ish distributions. It even works for bimodal distributions, though it's so vague that it barely matters.

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If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)