Class 7 Chapter 17: Data Handling

# Class 7 Chapter 17: Data Handling

Important Concepts and Formulas

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.      Arithmetic mean is obtained by dividing the sum of all observations by the number of observations. For a data set of n items, x1, x2, ... , xn, mean = (x1 + x2 + … xn)/n.

6.      To find the median of N items, arrange these N items in ascending order.

7.      If N is odd, the median = the middle term. For example, for {1, 3, 6, 8, 9, 10, 17}, the median = 8.

8.      If N is even, the median = the mean of the two middle terms. For example, for {4, 7, 10, 13, 15, 20}, the median = ½ (10 + 13) = 11.5.

9.      The mode of a data set is the value that occurs most often.

10. To represent data using a bar graph, we have to draw bars or rectangles of uniform width leaving equal space in-between the rectangles. The length of the bars represents the required information about the quantity.

11. Bar graphs can be easily drawn and drawing them is less time consuming.