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Classification of Data

The groups or classes of a classification can be done in various ways. Instead of classifying your books according to subjects — “History”, “Geography”, “Mathematics”, “Science” etc. — you could have classified them author-wise in an alphabetical order. Or, you could have also classified them according to the year of publication. The way you want to classify them would depend on your requirement. Likewise the raw data could be classified in various ways depending on the purpose in hand. They can be grouped according to time. Such a classification is known as a Chronological Classification.

Chronological Classification
In such a classification, data are classified either in ascending or in descending order with reference to time such as years, quarters, months, weeks, etc. The following example shows the population of India classified in terms of years. The variable 'population' is a Time Series as it depicts a series of values for different years.

Example 1: Population of India
Year Population (in crores)
1951
1961
1971
1981
1991
2001
35.7
43.8
54.6
68.4
81.8
102.7

 

In Spatial Classification the data are classified with reference to geographical locations such as countries, states, cities, districts, etc.

Example 2 shows the yield of wheat in different countries.

Courtesy NCERT Text book

Example 2
Yield of Wheat for Different Countries
Country Yield of wheat (kg/acre)
Africa
Britain
Canada
Denmark
England
India
1875
143
763
444
791
220

There are some characteristics that cannot be expressed quantitatively. Such characteristics are called Qualities or Attributes. For example, nationality, illiteracy, community, gender, marital status, etc. Such attributes cannot be measured. But these attributes can also be classified on the basis of either the presence or the absence of a qualitative characteristic. Such a classification of data on attributes is called a Qualitative Classification.

In the following example, we find population of a country is grouped on the basis of the qualitative variable “gender”. An observation could either be a male or a female. These two characteristics could be further classified on the basis of marital status (a qualitative variable) as given below.

Courtesy NCERT Text book

The classification at the first stage is based on the presence and absence of an attribute i.e. male or not male (female). At the second stage, each class — male and female, is further sub divided on the basis of the presence or absence of another attribute i.e. whether married or unmarried. On the other hand, characteristics like height, weight, age, income, marks of students, etc. are quantitative in nature. When the collected data of such characteristics are grouped into classes and such are called quantitative classification.

Example 4
Frequency Distribution of Marks in statistics of 100 Students

Table 3.1
Marks Frequency
0-5

5-10

10-15

15-20

20-25

25-30

30-35

35-40

40-45

45-50

2

13

16

6

11

18

17

6

3

8

Total 100

Example 4 shows quantitative classification of the data of marks in mathematics of 100 students given in Table 3.1 as a Frequency Distribution.




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