Measures of dispersion
Also called: Dispersion · Topic: Geographical Data: Sources, Compilation and Processing · NCERT: Class 12, Ch 2 "Data Processing"; Class 12, Ch 4 "Spatial Information Technology"
Meaning
Measures of dispersion show how spread out the values in a data set are, usually around a central value such as the mean. An average gives one middle figure, but it hides how far the values stray from it. Dispersion fills that gap. The main measures are the range, mean deviation and standard deviation. The coefficient of variation (SD ÷ mean × 100) is used to compare spread between data sets. These measures matter because two places can share the same average and still behave very differently.
Example
India's rainfall shows this clearly. In western Rajasthan and Kutch (Gujarat), the coefficient of variation of rainfall is above 50%. On the west coast and in the north-east it is below 25%. So the driest areas also have the least dependable rain, which matters for planning against drought.
Don't confuse with
- Measures of central tendency (mean, median, mode): these give the centre of the data. Dispersion tells you how widely the values spread around that centre.
Related concepts
- Range
- Mean deviation
- Standard deviation
- Coefficient of variation
- Measures of relationship
- Correlation coefficient