A classic measure of variability. Standard deviation is the square root of variance. Intuitively, standard deviation tells us how widely the values of a given variable are scattered around its average. The smaller the deviation the more observations are concentrated around the mean.

• Quartile deviation
• Average absolute deviation
• Square mean
• Typical area of variability
• Variance
• Pearson linear correlation coefficient
• Coefficient of variation of standard deviation

• Absolute measures of variation
• Structural point series
• Series of distribution with class intervals
• Detailed series
• Arithmetic mean
• Coefficient of variation