Chapter-10                               Organisation of Data



The process of grouping into classes and sub-classes according to similar characteristics is calledclassification.


(1)      To present the data into simple form.

(2)      To bring out clearly the point of similarity and dis-similarity.

(3)      To facilitate comparison.

(4)      To bring out relationship.

(5)      To prepare the basis for tabulation.

Methods of Classification

It can be grouped on the following basis :-

  • According to Time (Chloronological Classification)

The collected data are grouped with reference to the time such as year, month week etc.

Year            Production

2001            500

2002            400

  • Geographical Classification–

When the collected data are grouped with references to the location or geographical division, it is called geographical classification.

Countries     Production

A                 500

B                 400

C                 600

  • Qualitative Classification –

When data are grouped with references to quality or attributes which cannot be measured such as honesty, religion etc. is called qualitative classification.

(4)      Quantitative Classification –

When the collected data are grouped with reference to characteristics which can be measurable or numerically described such as height, weight, sales, import etc. it is called quantitative classification.



          If two variables quantities can be arranged side by side so that measurable differences in the one correspond with the measurable differences in the other.



(1)      Individual Series

Individual series is the one where items are listed simply after collection. Raw data can be arranged in –

  • Serial order
  • Ascending order
  • Descending order

The data arranged in ascending or descending order is calledData Array.

(2)      Discrete Series

          Any series represented by discrete variable is called discrete series.

Discrete variable/Discontinuous variable.

These are the variables which are exact or finite and are not normally fractions, e.g. test score in cricket match, children in a family, rooms in a house.

(3)      Continuous Series

Any series represented by continuous variable is called continuous series. The variables which can be broken down into infinite class intervals e.g. weight, height, income. All the fractional values are continuous variables.

Continuous Frequency Distribution are in 2 forms –

(i)       Inclusive Series

Under this method, upper class limit of the class intervals are included in the respective classes : – 5 – 9, 10 – 14, 15 – 19, 20 – 24 …….

(ii)      Exclusive Series

                   It is of two kinds

(a)      Exclusive Upper Limit:In this methodupper limits are excluded.

In this method, the upper limit of the classes interval is the lower limit of second class.

(b)      Exclusive Lower Limit: In this method, lower limit are excluded                                      from the class intervals.


Some Important Definition

Frequency :

The number of times given value is repeated is called frequency.

Class Frequency :The number of values in each of the class intervals is known as class frequency.

TotalFrequency :The sum of the frequencies is known as “total frequency”.Or the number of items in a data i.e. N is known as “total frequency”.

Frequency Distribution :

The distribution of the observation over the several values is called frequency distribution.

Upper and Lower Limit :The lowest and highest magnitude that forms the boundaries of the classes are known as lower and upper limit.

Mid points =

The mid value that lies half way between the lower and the upper limit.

Variables :

The quantity which varies from one individual to another is called variable.

Class size :

The difference between upper and lower limit is known as class size

= upper limit – lower limit.