Charts

Charts

Charts are means of diagrammatic representation of statistical data to make them easily understood. Examples of charts are:

Bar Chart:

Bar Charts are made up of spaced rectangular bars which are of equal width and whose lengths are proportional to the quantities they represent.

Use the example below to plot a bar chart.

Number of Cars Bought by the Johnson Company from 2014 – 2018

Years20142015201620172018
Number of Cars507010012010

Number of Cars Bought by the Johnson Company from 2014 – 2018

Pie Chart:

A pie chart is a simple circle which is divided into sections or sectors, each of which is proportional to the quantity of value it represents.

Example:

Eric, Alex, Fiona, and Sophie shared oranges in the following proportion: 16, 14, 18, and 12 respectively.
Use the above information to plot a pie chart.

Solution:

Total = 16 + 14 + 18 + 12 = 60 oranges
Eric: 16 oranges = \(\frac{16}{60} × \frac{360}{1}\) = 96°
Alex: 14 oranges = \(\frac{14}{60} × \frac{360}{1}\) = 84°
Fiona: 18 oranges = \(\frac{18}{60} × \frac{360}{1}\) = 108°
Sophie: 12 oranges = \(\frac{12}{60} × \frac{360}{1}\) = 72°

Histogram:

A histogram is a graphical representation of frequency distribution which is made up of rectangular bars that are joined together and they have their rectangles at the centre on the class mark (mid-point) of each interval.

Example:

1. The marks obtained by 62 students in an Economics test are as follows:

Marks20 – 2930 – 3940 – 4950 – 5960 – 6970 – 79
No. of candidates410161985

Note:

  • 20, 30, 40, 50, 60, and 70 are lower class limits.
  • 29, 39, 49, 59, 69, and 79 are upper class limits.
ScoreMid-Point
20 – 29\(\frac{(20 + 29)}{2} = \frac{49}{2} = 24.5\)
30 – 39\(\frac{(30 + 39)}{2} = \frac{69}{2} = 34.5\)
40 – 49\(\frac{(40 + 29)}{2} = \frac{89}{2} = 44.5\)
50 – 59\(\frac{(50 + 29)}{2} = \frac{109}{2} = 54.5\)
60 – 69\(\frac{(60 + 29)}{2} = \frac{129}{2} = 64.5\)
70 – 79\(\frac{(70 + 29)}{2} = \frac{149}{2} = 74.5\)

Score of Candidates of an Economics Test

Note that for this to be a histogram, the rectangular bars are supposed to be joined together.

Component Bar Chart:

A component bar chart is a diagrammatic representation in which each bar is sub-divided into two (2) or more components as the case may be.

Example:

The values of different types of accounts held in Nigerian banks for the period of 1984 – 1988 are as follows:

Year19841985198619871988
Savings Account1001201504060
Current Account6560208080
Fixed Account40308010070
Total205210250220210

Values of Different Accounts Held in by Different Banks from 1984 – 1988

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This is a lesson from the tutorial, Methods and Tools of Economic Analysis and you are encouraged to log in or register, so that you can track your progress.

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