Chebyshev's inequality - Wikipedia
https://en.wikipedia.org/wiki/Chebyshev's_inequalityIn probability theory, Chebyshev's inequality (also called the Bienaymé–Chebyshev inequality) guarantees that, for a wide class of probability distributions, no more than a certain fraction of values can be more than a certain distance from the mean. Specifically, no more than 1/k of the distribution's values can be k or more standard deviationsaway from the mean (or equivalently, over 1 − 1/k of the distribution's values are less than k standard deviations away from the mean)…
How to use Chebyshev's theorem to find the range of scores ...
www.quora.com › How-do-you-use-Chebyshevs-theoremChebyshev’s theorem is an amazing masterpiece of statistics which - unlike the empirical rule that applies to bell shaped distributions - holds regardless of the shape of the underlying distribution. 1 − 1 / k 2 (where k > 1) of the data lie within k standard deviations of the mean. So for instance to calculate the amount of data within 2 sd of the mean we put k = 2 which gives us 1 − 1 / 4 or 75% - we get the range of scores within 2 sd of the mean or 151 - 28 and 151 + 28.