Collection of Data NCERT Textbook PDF

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Chapter 2: Collection of Data

In the previous chapter, you have read about what is economics. You also studied about the role and importance of statistics in economics. In this chapter, you will study the sources of data and the mode of data collection. The purpose of collection of data is to show evidence for reaching a sound and clear solution to a problem.

In economics, you often come across a statement like this, “After many fluctuations the output of food grains rose to 132 million tonnes in 1978-79 from 108 million tonnes in 1970-71, but fell to 108 million tonnes in 1979-80. Production of food grains then rose continuously to 252 million tonnes in 2015-16 and touched 272 million tonnes in 2016–17.”

In this statement, you can observe that the food grains production in different years does not remain the same. It varies from year to year and from crop to crop. As these values vary, they are called variable. The variables are generally represented by the letters X, Y or Z. Each value of a variable is an observation.

For example, the food grain production in India varies between 108 million tonnes in 1970– 71 to 272 million tonnes in 2016-17 as shown in the following table. The years are represented by variable X and the production of food grain in India (in million tonnes) is represented by variable Y. Here, the values of these variables X and Y are the ‘data’, from which we can obtain information about the production of food grains in India.

To know the fluctuations in food grains production, we need the ‘data’ on the production of food grains in India for various years. ‘Data’ is a tool, which helps in understanding problems by providing information. You must be wondering where do ‘data’ come from and how do we collect these? In the following sections we will discuss the types of data, method and instruments of data collection and sources of obtaining data.


Statistical data can be obtained from two sources. The researcher may collect the data by conducting an enquiry. Such data are called Primary Data, as they are based on first hand information. Suppose, you want to know about the popularity of a filmstar among school students. For this, you will have to enquire from a large number of school students, by asking questions from them to collect the desired information.

The data you get, is an example of primary data. If the data have been collected and processed (scrutinised and tabulated) by some other agency, they are called Secondary Data. They can be obtained either from published sources such as government reports, documents, newspapers, books written by economists or from any other source, for example, a website.

Thus, the data are primary to the source that collects and processes them for the first time and secondary for all sources that later use such data. Use of secondary data saves time and cost. For example, after collecting the data on the popularity of the filmstar among students, you publish a report. If somebody uses the data collected by you for a similar study, it becomes secondary data.

Language English
No. of Pages13
PDF Size1.2 MB

NCERT Solutions Class 11 Statistics Chapter 2 Collection of Data

Question 1

Define primary data.


Primary data is the collection of data collected by the investigator for his own purpose for the first time. These are collected from the source of origin.

Question 2

Define secondary data.


According to Wessel, “Data collected by another person is known as secondary data”. It is known as secondary data as it has already been collected by somebody else. These data are accessible in the form of a published and unpublished report.

Question 3

What are the two sources of data?


The two sources of data are:

  • Primary source
  • Secondary source

Question 4

Mention two sources of secondary data.


The two sources of secondary data are:

  • Government publication
  • Semi-government publication

Question 5

In what parameters is the statistical information published in the census of India?


The statistical information is published in the following parameters in the census of India[1] 

  • Population projection
  • Sex composition of a population
  • Density of population
  • Size, growth rate, and distribution of people in India

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