## 4 January 2014

• Data is a collection of numbers gathered to get some information.
• To get the required information, all observations should be recorded.
• Tally marks are used to organise the observations. Record every observation by a vertical mark, but every fifth observation should be recorded by a mark across the four earlier marks, like this:.
• We depict each observation with the help of tally marks.
For example, we have a group of persons and their sizes of shoes.  The tabular form representing the tally marks is as shown here.

### Pictograph

A picture that visually helps us to understand data is called a pictograph.  A pictograph represents data in the form of pictures, objects or parts of objects.
Eg:

In real life, pictographs are used by newspapers and magazines to attract the attention of the readers.  A pictograph helps us to answer questions on the data at a glance.  To draw pictographs, we use symbols to represent a certain number of things or items.
For example, represents 100 bulbs.
The key for a pictograph tells the number that each picture or symbol represents.

### Bar graphs

Bar graphs or bar diagrams are  helpful in  representing the data visually. In bar graphs or bar diagrams, bars of equal width are drawn horizontally or vertically with equal spacing between them.
The length of each bar represents the required information.     Choosing an appropriate scale for a bar graph is important.  Scale means the number used to represent one unit length of a bar.  For example, the scale for the bar graph shown here is 1 unit length = 100 children.

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