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CBSE - VIII

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Data Handling

We know that **data **is a collection of observations. Visual representation of **data** will help us to understand it better and remember the facts easily.

The word ‘**data’** means **collection of information** in the form of numerical figures, or a set of given facts.

Examples:

- The marks obtained by 10 students of a class in a test are:

76, 83, 95, 100, 56, 32, 80, 67, 75, 46 - The following table gives the data regarding the favourite game of 100 students of a school:

Sports | Cricket | Football | Tennis | Badminton |

Number Of Students | 40 | 30 | 25 | 5 |

When some information is **collected and presented randomly**, then it is called **raw data**. A **data** classified into groups is called **grouped data**.

Data in raw form can be represented in the form of **pictures** and **diagrams**. It makes the given data **attractive** to the observer. Also, it is **easy to understand** and to compare it with other information.

Some commonly used diagrams to **represent numerical data** are:

**Pictographs****Bar graph****Double bar graph****Pie-diagrams or Pie-charts**

**Pictographs** represent data through appropriate** pictures**. In pictographs, the same type of **symbol** or **picture** is used to represent the data. Each symbol is used to represent a certain value, and this is mentioned clearly in the graph. For example, one symbol may represent 25 students.

The following pictograph represents the number of students coming to a college by different means of transport:

A** representation of data** with the help of **bars or rectangles** in a **diagram** is called a **bar graph** or a **bar diagram**.

Here, each **bar** represents only one value of the data, and hence, there are as many bars as the number of values in the data. The **length** or **height** **of a bar** indicates the value of the item. The **width of a bar** and the **gap between the bars** is kept uniform to make the diagram look neat.

The following bar graph represents the production of rice in different years:

Sometimes, organising data becomes a tedious process. In such cases, we group the raw data. We write the groups as intervals. Each group is called a **class interval. **The **class interval** will have a lower class limit and an upper class limit.

The difference between the upper class limit and the lower class limit is called the width or size of the **class interval**. The number of times a particular item appears within a particular class interval is called **frequency**.

The span of a class interval is called the **width **or** size **of the** class** **interval**.

We fill up the rows with tally marks and will count the total number of tally marks in each group. The number of tally marks in each group is listed in the frequency column. The completed table is called the **frequency distribution table**. With the data in a table, we can draw a graph.

A graph showing two sets of data simultaneously is called a double bar graph. It is useful for comparing two sets of data.

The following graph shows the strength of boys and girls in a school in different years:

A **pie diagram** or a **pie chart** is a circle divided into several **sectors**. The **circle** represents the total value of the given data, and the sectors represent the proportion of the components of the total.

It is also called an **angular diagram** or a **circular diagram**.

The monthly expenditure on various items of a family is given below.

Item | Food | House Rent. | Misc. | School Fees |

Amount Spent | Rs. 2500 | Rs. 2700 | Rs. 2400 | Rs. 1400 |

Its representation in a pie diagram is as shown.