There are various methods of measuring the dispersions of a series which can be broadly classified into three categories as under:
- Method of limits
- Method of computations
- Method of graphs.
1. Dispersion by the method of limits
Under this method, the dispersion of a series are studied by taking into account the extreme limits of certain factors viz. value, quartiles, deciles, percentiles etc. of a series.
The following measures of dispersion come under this method : (i) Range, (ii) Inter-Quartile Range (iii) Semi-inter Quartile Range or Quartile Deviation, (iV) Decile Range, and (v) Percentile Range.
2. Dispersion by the method of computation
Under this method, the dispersal character of a series is studied through the process of computation. The following measures come under this calss:
3.Dispersion by the method of graphs
Under this method, the dispersion of a series is studied by drawing certain suitable, graphs, viz. Lorenz Curve: