Diagrams Types
One-dimensional bar diagrams:
These bar diagrams are the most common type of diagrams used in practice. A bar is a thick line whose width is represented merely for attention.
The special advantages of bar diagrams are the following:
(i) They are readily understood even by those who are not accustomed to reading the charts.
(ii) They possess the outstanding advantage that they are simpler and the easier to make.
(iii) When a large no. of items is to be compared they are the only form that can be used effectively.
The important types of one-dimensional bar diagrams are:
(a) Simple bar diagrams: A simple bar diagram is used to show only one variable.
Illustration: Following table gives the birth rate per thousand of various countries over a certain period:
|
Country
|
Birth rate
|
Country
|
Birth rate
|
|
India
|
33
|
China
|
40
|
|
Germany
|
16
|
New Zealand
|
30
|
|
U.K.
|
20
|
Sweden
|
15
|
(b) Sub-divided bar diagrams: In a sub-divided bar diagram each bar showing the magnitude of a given phenomenon is further sub-divided in its various components.
(c) Multiple bars: In a multiple bar diagram two or more sets of interrelated data are shown.
(d) Percentage bars: The percentage bars are particularly useful in statistical work that requires the portrayal of relative changes in data.
Two-dimensional bar diagrams:
As distinguished from one-dimensional bar diagrams in which only the length of the bar is taken into account, in two-dimensional diagrams the length as well as the width of the bars is considered.
The important types of Two-dimensional bar diagrams are:
(a) Rectangles: - This form is quite popular, as the area of a rectangle is equal to the product of its length and width while constructing such a diagram both length & width are considered.
Illustration: the following data shows the monthly expenditure (in $) of two families A and B:
|
Items of expenditure
|
Family A
|
Family B
|
|
Food
|
16000
|
12000
|
|
Clothing
|
8000
|
6000
|
|
Rent
|
6000
|
5000
|
|
Light and fuel
|
2000
|
1000
|
|
Miscellaneous
|
8000
|
6000
|
Represent the above data by a suitable percentage diagram.
Solution: convert the given figures into percentage as follows:
|
Items of expenditure
|
$(family A)
|
% (family A)
|
Cum% (family A)
|
$ (family B)
|
Y (family B)
|
Cum % (family B)
|
|
Food
|
16000
|
|
40
|
12000
|
40.00
|
40.00
|
|
Clothing
|
8000
|
20
|
60
|
6000
|
20.00
|
60.00
|
|
Rent
|
6000
|
15
|
75
|
5000
|
16.67
|
76.67
|
|
Light and fuel
|
2000
|
5
|
80
|
1000
|
3.33
|
80.00
|
|
Miscellaneous
|
8000
|
20
|
100
|
6000
|
20.00
|
100.00
|
|
total
|
40000
|
100
|
|
30000
|
100
|
|
(b) Squares: - The rectangular method of diagrammatic presentation is quite difficult to use where the values of items vary widely. For e.g. If in the illustration given above the number of units sold of commodity A & B are 20 & 240 respectively. Therefore the width of the rectangles would be in the ratio of 5:60 or 1:12.
(c) Circles: Another way of preparing a two-dimensional diagram is in the lord of the circles.