## 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**

### 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**