$$\mathbf{1}-\frac{\mathbf{1}}{k^{2}}$$
For example, at least $1-1 / 2^{2}=3 / 4$ of any set of numbers lie within 2 standard deviations of the mean. Similarly, for any probability distribution, the probability that a number will lie within $k$ standard deviations of the mean is at least $1-1 / k^{2}$ .
For example, if the mean is 100 and the standard deviation is 10, the probability that a number will lie within 2 standard deviations of 100, or between 80 and 120, is at least Use Chebyshev’s theorem to find the fraction of all the numbers of a data set that must lie within the following numbers of standard deviations from the mean.
$$5$$