Types (Bases) of Classification

Data can be classified on four standard bases, according to the nature of the characteristic used.

1. Geographical (spatial) classification. Data is classified according to place or area — states, districts, cities, regions. Example: population of Odisha classified district by district. The classes are usually arranged alphabetically or by size.
2. Chronological (temporal) classification. Data is classified according to time — years, months, weeks. Example: a company's annual sales for 2018 to 2024. Data classified over time in this way forms a time series.
3. Qualitative classification (classification by attributes). Data is classified according to some quality or attribute that cannot be measured numerically — sex, literacy, religion, occupation, marital status.
   • Simple classification (dichotomous / two-fold): the population is divided by the presence or absence of a single attribute — e.g. literate vs illiterate.
   • Manifold classification (multiple): the population is divided by more than one attribute at a time — e.g. first by sex (male/female), then each of those by literacy (literate/illiterate), giving four groups.
4. Quantitative (numerical) classification. Data is classified according to a characteristic that can be measured numerically — height, weight, income, marks, age. The characteristic being measured is called a variable. A quantitative classification of data into value-groups with their frequencies is a frequency distribution (§7). …