2. Classification
The collected data or raw data or ungrouped data are always in an un
organised form and need to be organised and presented in meaningful and
readily comprehensible form in order to facilitate further statistical analysis.
It is, therefore, essential for an investigator to condense a mass of data into
more and more comprehensible and assimilable form.
The process of grouping into different classes or sub classes according to
some characteristics is known as classification,
Tabulation is concerned with the systematic arrangement and presentation of
classified data. Thus classification is the first step in tabulation.
Eg: Letters in the post office are classified according to their destinations viz., Delhi,
Madurai, Bangalore, Mumbai etc.,
3. Objects of Classification
The following are main objectives of classifying the data:
1. It condenses the mass of data in an easily assimilable form.
2. It eliminates unnecessary details.
3. It facilitates comparison and highlights the significant aspect of
data.
4. It enables one to get a mental picture of the information and helps
in drawing inferences.
5. It helps in the statistical treatment of the information collected.
4. Types of classification
Statistical data are classified in respect of their characteristics.
Broadly there are four basic types of classification namely
a) Chronological classification
b) Geographical classification
c) Qualitative classification
d) Quantitative classification
5. a) Chronological classification: In chronological
classification the collected data are arranged according
to the order of time expressed in years, months, weeks,
etc., The data is generally classified in ascending order
of time.
b) Eg: The estimates of birth rates in India during 1970 – 76 are
Year 1970 1971 1972 1973 1974 1975 1976
Birth Rate 36.8 36.9 36.6 34.6 34.5 35.2 34.2
6. b) Geographical classification: In this type of classification the
data are classified according to geographical region or place. For
instance, the production of paddy in different states in Iraq, production
of wheat in different countries etc.,
Eg:
Country America China Denmark France Iraq
Yield of wheat 1925 893 225 439 862
in (kg/acre)
7. c) Qualitative (categorical) classification: In this type of
classification, data are classified on the basis of same attributes or
quality like sex, literacy, religion, employment etc.,
Such attributes cannot be measured along with a scale.
Eg: if the population to be classified in respect to one attribute, say
sex, then we can classify them into two names that of males and
females.
Similarly, they can also be classified into ‘married or ‘ single’ on the
basis of another attribute ‘marital status’.
8. Thus when the classification is done with respect to one
attribute, which is dichotomous in nature, two classes are
formed, one possessing the attribute and the other not
possessing the attribute. This type of classification is
called simple or dichotomous classification.
9. d) Quantitative (numerical) classification: Quantitative
classification refers to the classification of data according to some
characteristics that can be measured such as height, weight, etc.,
Eg: the group of children may be classified according to weight as
given below.
Weight (in kg) No of children
5-10 50
10-15 200
15-20 260
20-25 360
10. PRIMARY RULES OF CLASSIFICATION
The process of arranging data in groups and classes
according to their similar attributes is an important task
for which many important considerations have to be taken
into account.
i. The number of classes should not be excessive.
ii. There should not be any ambiguity in the definition of
classes.
11. iii. All the classes should preferably have equal width or length.
iv. Magnitude of the class intervals should be as far as possible
in multiples of 5 like 10, 15, 20, 25 etc.
v. The class intervals should as far as possible is of equal size.
vi. The classification must be suitable for the object of inquiry.
vii. The classification should be flexible and items included in
each class must be homogeneous.
12. Tabulation
Tabulation is the process of summarizing classified or grouped data
in the form of a table so that it is easily understood and an investigator
is quickly able to locate the desired information.
A table is a systematic arrangement of classified data in columns and
rows.
Tabulation refers to a logical data presentation, wherein raw data is
summarized and displayed in a compact form, i.e. in statistical tables.
In other words, it is a systematic arrangement of data in columns and
rows, that represents data in concise and attractive way.
13. Thus, a statistical table makes it possible for the
investigator to present a huge mass of data in a detailed
and orderly form.
It facilitates comparison and often reveals certain
patterns in data which are otherwise not obvious.
Classification and Tabulation , as a matter of fact, are not
two distinct processes. Actually they go together.
14. Major Objectives of Tabulation
1. To simplify the complex data
2. To facilitate comparison
3. To economize the space
4. To draw valid inference / conclusions
5. To help for further analysis
15. Differences Between Classification and Tabulation
The process of arranging data into different categories, on
the basis of nature, behavior, or common characteristics is
called classification.
A process of condensing data and presenting it in a compact
form, by putting data into statistical table, is called tabulation.
Classification of data is done after data collection process is
completed. On the other hand, tabulation follows classification.
16. Data classification is based on similar attributes and variables of the
observations. Conversely, in tabulation the data is arranged in rows
and columns, in a systematic way.
Classification of data is performed with the objective of analysing
data in order to draw inferences. Unlike tabulation, which aims at
presenting data, to ensure easy comparison of various figures.
In classification, data is bifurcated into categories and sub-
categories while in tabulation data is divided into headings and sub-
headings.
17. CONTENTS OF A TABLE
i. Table number: Each table should be numbered should be easy
identification and future reference.
ii. Title: Every table should have a title which is generally given at
the top of the table in the center.
iii. Captions: A caption generally has a main heading and a number
of small subheadings.
iv. Stubs: It refers to the headings of the horizontal rows and return
on the left hand side of the row.
18. v. Body: It contains the statistical data which have to be presented.
vi. Headnote: It refers to the data contained in the major part of the
table and it is placed below the title of the table.
vii. Footnote: Footnotes are given below the table and are meant to
clarify anything which is not clear from the heading, title, stubs
and caption.
