Standard Deviation Standard deviation is a measure of the dispersion of a data set. In more layman's terms, it measures the general variation of the mean value and the other values in the data set. A small standard deviation means that the values tend to be very close to the mean. A larger standard deviation means the data is generally farther away from the mean. Bell curves, like the one shown below of the normal distribution, use standard deviation 34.19 341% 2.1 2.1% 01% 0.1% 13 6% 13 6% -30-20-10 1 2 3 In the bell curve, represents the mean, and represents the standard deviaton. The equation for caclulating standard deviation is shown below: N is the number of elements in the data set x is the th number in the data set. is the mean. In English