# 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

 Years 2014 2015 2016 2017 2018 Number of Cars 50 70 100 120 10

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:

 Marks 20 – 29 30 – 39 40 – 49 50 – 59 60 – 69 70 – 79 No. of candidates 4 10 16 19 8 5

Note:

• 20, 30, 40, 50, 60, and 70 are lower class limits.
• 29, 39, 49, 59, 69, and 79 are upper class limits.
 Score Mid-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:

 Year 1984 1985 1986 1987 1988 Savings Account 100 120 150 40 60 Current Account 65 60 20 80 80 Fixed Account 40 30 80 100 70 Total 205 210 250 220 210

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