https://en.wikipedia.org/wiki/Chebyshev%27s_inequality
Pr(∣X−μ∣≥kσ)≤1k2\Pr(|X-\mu |\geq k\sigma )\leq {\frac {1}{k^{2}}}Pr(∣X−μ∣≥kσ)≤k21
Related to Markov's inequality
See also Chernoff bound