Inadequacy of Central Tendency:
Considers two groups below
Group I Group II
42 10
45 22
50 (the Mean) 50 (the Mean)
55 78
58 90
- The numbers in Group I are concentrated about their mean, whereas those of Group II are widely scattered.
- The measures of Central Tendency are therefore insufficient. They must be supported by or supplemented with other measures.
- A measure of Dispersion is designed to state the extent to which the individual measures differ on the average from the mean.
- In measuring dispersion we are interested in the amount of the variation or its degree but not in the direction.
- A measure of 4 inches below the mean has just as much dispersion as a measure of 4 inches above the mean.
- The amount of variability, or absolute variability, will be expressed in concrete units, the same units that are used for the original variates,, while the degree or relative variability, will be expressed ratios.
- A measure of absolute variation is useful in describing a single frequency distribution, but if two different distributions are to be compared, difficulties are encountered.
