ABSTRACT
This chapter discusses several measures of variability. These include several forms of the range, the variance, and the standard deviation. The chapter also discusses how to compute each. The range is the distance from the upper limit of the highest score to the lower limit of the lowest score. The variance is the mean of the squared deviations from the mean. The variance is a very powerful measure of variability and is widely used throughout measurement and statistics. However, it is based on a squared scale and is, therefore, difficult to interpret directly. The standard deviation is the square root of the mean of the squared deviations from the mean. The variance and the standard deviation are probably the two most often used measures of variability. Frequency distributions can be described by three characteristics: their form (shape), central tendency, and variability. A variety of variability measures have been developed.
