In order to understand the concept of dispersion, let us consider some important definition of dispersion.
- The Degree to which numerical data tend to spread about an average value is called the variation or dispersion of the data (Spiegel)
- The measurement of scatterness of the mass of figures in a series about an average is called measures of variation or dispersion (Simpson and Kafka)
- Dispersion or spread is the degree of the scatter or variation of the variables about a central value (Brook and Dick)
From the above definitions, it is clear that the word, dispersion (also termed as variation or spread or scatter) is used to denote the degree of heterogeneity in the data. It is an important characteristic indicating the extent to which observations vary among themselves. A measure of dispersion describes the spread or scattering of individual values around the central value. It gives an average of the differences of various observations from a central value (an average). Thus, the significance of an average is determined in the light of dispersion.
