Chebyshev's inequality - Wikipedia
https://en.wikipedia.org/wiki/Chebyshev's_inequalityMarkov's inequality states that for any real-valued random variable Y and any positive number a, we have Pr(|Y| > a) ≤ E(|Y|)/a. One way to prove Chebyshev's inequality is to apply Markov's inequality to the random variable Y = (X − μ) with a = (kσ) . It can also be proved directly using conditional expectation: Chebyshev's inequality then follows by dividing by k σ .
Chebyshev's inequality - Wikipedia
en.wikipedia.org › wiki › Chebyshev&The rule is often called Chebyshev's theorem, about the range of standard deviations around the mean, in statistics. The inequality has great utility because it can be applied to any probability distribution in which the mean and variance are defined. For example, it can be used to prove the weak law of large numbers .