Everyday we come across a lot of information in the form of facts, numerical figures, tables, graphs, etc. These are provided by newspapers, televisions, magazines and other means of communication.

These may relate to cricket batting or bowling averages, profits of a company, temperatures of cities, expenditures in various sectors of a five year plan, polling results, and so on.

These facts or figures, which are numerical or otherwise, collected with a definite purpose are called data. Data is the plural form of the Latin word datum.

Of course, the word ‘data’ is not new for you. You have studied about data and data handling in earlier classes.

Our world is becoming more and more information oriented. Every part of our lives utilities data in one form or the other.

So, it becomes essential for us to know how to extract meaningful information from such data. This extraction of meaningful information is studied in a branch of mathematics called `"Statistics."`

The word ‘statistics’ appears to have been derived from the Latin word ‘status’ meaning ‘a (political) state’. In its origin, statistics was simply the collection of data on different aspects of the life of people, useful to the State.

Over the period of time, however, its scope broadened and statistics began to concern itself not only with the collection and presentation of data but also with the interpretation and drawing of inferences from the data.

Statistics deals with collection, organisation, analysis and interpretation of data. The word ‘statistics’ has different meanings in different contexts. Let us observe the following sentences:

1. May I have the latest copy of ‘Educational Statistics of India’.

2. I like to study ‘Statistics’ because it is used in day-to-day life.

In the first sentence, statistics is used in a plural sense, meaning numerical data.

These may include a number of educational institutions of India, literacy rates of various states, etc.

In the second sentence, the word ‘statistics’ is used as a singular noun, meaning the subject which deals with the collection, presentation, analysis of data as well as drawing of meaningful conclusions from the data.

In this chapter, we shall briefly discuss all these aspects regarding data.

Let us begin with an exercise on gathering data by performing the following activity.

`color { blue} text(Activity 1) :` Divide the students of your class into four groups. Allot each group the work of collecting one of the following kinds of data:

(i) Heights of 20 students of your class.

(ii) Number of absentees in each day in your class for a month.

(iii) Number of members in the families of your classmates.

(iv) Heights of 15 plants in or around your school.
Let us move to the results students have gathered. How did they collect their data in each group?

(i) Did they collect the information from each and every student, house or person concerned for obtaining the information?

(ii) Did they get the information from some source like available school records?

In the first case, when the information was collected by the investigator herself or himself with a definite objective in her or his mind, the data obtained is called primary data.

In the second case, when the information was gathered from a source which already had the information stored, the data obtained is called secondary data.

Such data, which has been collected by someone else in another context, needs to be used with great care ensuring that the source is reliable.

By now, you must have understood how to collect data and distinguish between primary and secondary data.