For a Gaussian, 2 times the square root of the quantity 2 times natural log of 2, times this quantity, equals the full width at half max.
In the analysis of stock prices, the upper and lower Bollinger bands are used to visualize this measure for a security.  Chebyshev's inequality places a 1 over k-square upper bound on the proportion of observations that have a k-tuple value for this quantity. The correlation of variables X and Y is defined as the covariance of X and Y divided by the products of these values for X and Y. T and Z-scores signify multiples of this value for an observation, and this quantity is the square root of the expected value of the square of the distribution minus the mean. For a Gaussian, 2 times the square root of the quantity 2 times natural log of 2, times this quantity, equals the full width at half max. For 10 points, identify this quantity which describes the degree to which a distribution is spread out.
In the analysis of stock prices, the upper and lower Bollinger bands are used to visualize this measure for a security.  
standard deviation