of the observations fall within 1 standard deviation of the mean, that is, between µ-σ and µ+σ .
of the observations fall within 2 standard deviations of the mean, that is, between µ-2σ and µ+2σ.
of the observations fall within 3 standard deviations of the mean, that is, between µ-3σ and µ+3σ .
The 68-95-99.7% Rule
All normal density curves satisfy the following property which is often referred to as the Empirical Rule.
Thus, for a normal distribution, almost all values lie within 3 standard deviations (or any measure of volatility) of the mean.
My observation has been that each segment within any given Normal Gaussian Distribution, consists of at least one Normal Gaussian Distribution, and in turn is a member of a large Normal Gaussian Distribution. Fractals? Or Billions!