Class 8 Chapter 17: Data Handling and graphs

# Class 8 Chapter 17: Data Handling and graphs

## Important Concepts and Formulas of Data Handling and Graphs

1.      Data is a collection of numbers, figures, names or any items collected to give some information.

2.      The data which has not been organized is called raw data.

3.      Data can be collected by the following methods: Taking measurements in experiments, Observing outcomes of events, conducting surveys, reading statistical publications.

4.      The difference between the highest and the lowest observations is called the range of the data. Range = Value of the highest observation – Value of the lowest observation.

5.      When numerical data is represented as columns then it is called a bar graph. It is also known as column graph.

6.      The double bar graph helps us to compare or present more than one kind of information.

7.      Large data needs to be organized in groups (classes).

8.      The difference between the upper limit and lower limit of a class is called the class width or size of the interval.

9.      In a histogram, the heights of various bars are proportional to their frequencies and the bars are drawn without any gaps between them.

10. A pie chart is used to show the relationship between a whole and its parts.

11. When the numerical data is represented by a sector of a circle, it is called pie chart or pie graph. The angle of the sector depends upon the value of that item in the data. Angle of sector = (Value of item/Sum of all items) × 360°.

12. The line graph displays those data that changes over a period of time. A line graph consists of bits of line segments joined consecutively.

13. A linear relationship is a relationship between two variables in which the amount of both the variables increases or decreases by same quantity. Linear graph is a graph that explains a linear relationship.

14. Variables used in experiments are of two types—dependent variable and independent variable.

15. An independent variable is a variable that is not changed by the other variables. A dependent variable depends on other factors.

16. We determine the position of a point in the cartesian plane by fixing its coordinates.

17. Two mutually perpendicular axes intersect at a point called the origin. Coordinates of the origin are (0, 0).

18. The coordinate axes divide the plane of a graph paper into four regions called quadrants.