Back to: MATHEMATICS JSS3

**Welcome to Class !!**

*We are eager to have you join us !!*

*In today’s Mathematics class, We will be talking about Statistics. We hope you enjoy the class!*

**Types of Presentation**

A good **presentation **can make statistical data easy to read, understand and interpret. Therefore it is important to present data clearly.

- There are two main ways of presenting data: presentation of numbers or values in
**lists**and**tables;** - A presentation using
**graphs,**i.e. pictures. We use the following examples to show various kinds of presentation.

An English teacher gave an essay to 15 students. |

*She graded the essays from A (very good), through B, C.D, E to f (very poor). The grades of the students were:*

*B, C, A, B, A, D, F, E, C, C, A, B, B, E, B*

**Lists and tables**

#### Rank and order list

**Rank order **means in order from highest to lowest. The 15 grades are given in rank order below:

A, A, A, B, B, B, B, C, C, C, E, E, F

Notice that all the grades are put in the list even though most of them appear more than once. The ordered list makes it easier to find the following: the highest and lowest grades; the number of students who got each grade; the most common grade; the number of students above and below each grade; and so on.

##### Frequency table

**Frequency **means the number of times something happens. For example, three students got grade A.

The frequency of grade A is three. A **frequency table **gives the frequency of each grade.

Grade |
A |
B |
C |
D |
E |
F |

frequency |
3 | 5 | 3 | 1 |
2 | 1 |

**Graphical presentation**

In most cases, a picture will show the meaning of statistical data more clearly than a list of or table or numbers. The following methods of presentation give the data of the example in a picture, or **graph **form.

**Pictogram**

A **pictogram **uses pictures or drawings to give a quick and easy meaning to statistical data.

**Bar chart**

A bar chart represents the data as horizontal or vertical bars. The length of each bar is proportional to the amount that it represents.

There are 3 main types of bar charts.

Horizontal bar charts, vertical bar chart and double bar charts.

When constructing a bar chart it is important to choose a suitable scale to represent the frequency.

**Pie Chart**

**Pie charts** are useful to compare different parts of a whole amount. They are often used to present financial information. E.g. A Company’s expenditure can be shown to be the sum of its parts including different expense categories such as salaries, borrowing interest, taxation and general running costs (i.e. rent, electricity, heating etc.).

A pie chart is a circular chart in which the circle is divided into sectors. Each sector visually represents an item in a data set to match the amount of the item as a percentage or fraction of the total data set.

**Example**

A family’s weekly expenditure on its house mortgage, food and fuel are as follows:

Expenses |
N |

Mortgage | 300 |

Food | 225 |

Fuel | 75 |

Draw a pie chart to display the information.

**Solution**

The total weekly expenditure = N300 + N225 + N75 = N600

We can find what percentage of the total expenditure each item equals.

Percentage of weekly expenditure on:

Mortgage = $\frac{300}{600}$ X 100% = 50%

Food = $\frac{225}{600}$ X 100% = 37.5%

Fuel = $\frac{75}{600}$ X 100% = 12.5%

To draw a pie chart, divide the circle into 100 percentage parts. Then allocate the number of percentage parts required for each item.

**Note**

It is simple to read a pie chart. Just look at the required sector representing an item (or category) and read off the value. For example, the weekly expenditure of the family on food is 37.5% of the total expenditure measured.

A pie chart is used to compare the different parts that make up a whole amount.

** **

**EVALUATION**

The following is a rank order list of an exam result: 87, 82, 78, 76, 75, 70, 66, 64, 59, 59, 59, 51, 49, 48, 41.

- How many students took the exam?
- What was the highest rank?
- What was the lowest rank?
- What is the mark of the student who came 6th?
- What is the position of the student who got 76 marks?
- Three students got 59 marks. What is their position?
- How many students got less than 75 marks?

*We have come to the end of this class. We do hope you enjoyed the class?*

*Should you have any further question, feel free to ask in the comment section below and trust us to respond as soon as possible.*

*In our next class, we will be talking about Factorization involving Common Factors. We are very much eager to meet you there.*

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