1. Dr. M. MARIAPPAN
M.Sc., M.Phil., M.Ed., Ph.D.
Assistant Professor,
Department of Zoology,
Government Arts College,
Melur – 625 106
2. In diagrammatic presentation, the data are
presented in the form of diagrams such as
bars, circles, maps, cartograms, etc.
A diagram is a drawing or a design to explain
the data.
Diagram is becoming more popular because
they are attractive and meaningful.
DIAGRAMS
3. Significance of Diagrams:
Diagrams simplify complexity of data.
They create more effects on the minds of the
observers.
They save time and labour.
They provide more information.
They make comparison easily.
Limitations of a Diagram:
It is only a supplement to the tabular presentation.
Diagram shows only approximate values.
It cannot be analyzed further.
Small differences cannot to be studied.
4. Kinds of Diagrams
1 • Line Diagram
2 • Bar Diagram
3 • Pie Diagram
4 • Pictogram
5 • Cartogram
5. a) LINE DIAGRAM:
In line diagram, the statistical data represent in the
form of Straight lines.
Height of line indicates the size of data.
The distances between lines are kept in uniform.
Line diagram is not attractive.
(Eg.) Data shows the yield of a fish farm.
Types of Fishes
Yield
(Kg.)
Common Carp 300
Rohu 250
Mirgal 200
Tilapia 150
6.
7. b) Bar Diagram:
The data are drawn in the form of rectangles or bars
is known as Bar Diagram.
Vertical rectangles are drawn as per the height of
frequency.
Equal space is given between the rectangles.
Width of each rectangle should be also same.
The bar diagram is of the following types:
1) Simple Bar Diagram
2) Multiple Bar Diagram
3) Component Bar Diagram
4) Percentage Bar Diagram
8. I. Simple Bar Diagram:
In simple bar diagram has vertical rectangles at
regular intervals.
Height of each rectangle indicate the data.
Width of each rectangle should be the same.
It is one-dimensional diagram.
(Eg.) Data about blood group among the students.
Blood Group No. of Students
A 20
B 40
AB 10
O 5
9.
10. II. Multiple Bar Diagram:
In multiple bar diagram, two or more bars drawn side by
side.
It is also called Compound bar diagram.
Height of the bar represents the data value.
Width should be same and equal space should be given.
It is one-dimensional diagram.
(Eg.) Data about blood groups of boys and girls.
Blood Group
No. of Students
Boys Girls
A 40 35
B 35 25
AB 20 10
O 10 5
11.
12. III. Component Bar Diagram:
In component bar diagram, each rectangle is subdivided
into segments as per data.
It is also called Subdivided bar diagram.
Height of the bar represents the data value.
Width should be same and equal space should be given.
(Eg.) Data shown Blood group in three years of students.
Blood
Group
No. of Students
I – Year II – Year III - Year
A 6 4 5
B 20 15 19
AB 10 10 10
O 9 6 8
13.
14. IV. Percentage Bar Diagram:
The rectangles are drawn as per the percentage of the
data.
All the rectangles are equal in height.
Equal spacing is given between the bars.
15. c) Pie Diagram:
The data are presented in the form of a Circle.
The circle area is subdivided into sectors by radi as
per angles (degrees).
Pie diagram is also called as Circle or Angular
Diagram.
It is two – dimensional diagram.
Procedure:
The surface area of circle is known as 360º (Degrees).
Convert the given value of the components of an item
into degree. This is done by dividing each value by the
total and multiplying by 360.
16. In the pie chart largest value remains at the top and
other in sequence running clockwise.
The degree for each value is measured with a
protractor.
(Eg.) Marks obtained in test by a person of GAC, Melur
Invertebrata Chordata Cell Biology
65 60 55
Total Number of Components = 65 + 60 + 55 = 180
18. d) Pictogram:
In pictogram, data are drawn in the form of pictures.
Number of pictures is equal to the values.
Pictures are draw side horizontally or vertically.
It is widely used in public and private sector.
(Eg.) Sales of fish (in tons) in last three years.
Year 2016 2017 2018
Sales of Fish
(in tons)
1000 2000 3000
