NCERT Book Class 7 Maths Data Handling

Data Handling

3.1 INTRODUCTION

In your previous classes, you have dealt with various types of data. You have learnt to collect data, tabulate and put it in the form of bar graphs. The collection, recording and presentation of data help us organise our experiences and draw inferences from them. In this chapter, we will take one more step towards learning how to do this. You will come across some more kinds of data and graphs. You have seen several kinds of data through newspapers, magazines, television and other sources. You also know that all data give us some sort of information. Let us look at some common forms of data that you come across:

3.2 COLLECTING DATA

The data about the temperatures of cities (Table 3.1) can tell us many things, but it cannot tell us the city which had the highest maximum temperature during the year. To find that, we need to collect data regarding the highest maximum temperature reached in each of these cities during the year. In that case, the temperature chart of one particular date of the year, as given in Table 3.1 will not be sufficient.

This shows that a given collection of data may not give us a specific information related to that data. For this we need to collect data keeping in mind that specific information. In the above case the specific information needed by us, was about the highest maximum temperature of the cities during the year, which we could not get from Table 3.1

Thus, before collecting data, we need to know what we would use it for. Given below are a few situations.

You want to study the

– Performance of your class in Mathematics.

– Performance of India in football or in cricket.

– Female literacy rate in a given area, or

– Number of children below the age of five in the families around you..

What kind of data would you need in the above situations? Unless and until you collect appropriate data, you cannot know the desired information. What is the appropriate data for each? Discuss with your friends and identify the data you would need for each. Some of this data is easy to collect and some difficult.

3.3 ORGANISATION OF DATA

When we collect data, we have to record and organise it. Why do we need to do that? Consider the following example. Ms Neelam, class teacher wanted to find how children had performed in English. She writes down the marks obtained by the students in the

following way:

23, 35, 48, 30, 25, 46, 13, 27, 32, 38

In this form, the data was not easy to understand. She also did not know whether her impression of the students matched their performance.

3.4 REPRESENTATIVE VALUES

You might be aware of the term average and would have come across statements involving the term ‘average’ in your day-to-day life:

• Isha spends on an average of about 5 hours daily for her studies.
• The average temperature at this time of the year is about 40 degree Celsius.
• The average age of pupils in my class is 12 years.
• The average attendance of students in a school during its final examination was 98 per cent.

Many more of such statements could be there. Think about the statements given above.

Do you think that the child in the first statement studies exactly for 5 hours daily?

Or, is the temperature of the given place during that particular time always 40 degrees?

Or, is the age of each pupil in that class 12 years? Obviously not.

Then what do these statements tell you?

By average we understand that Isha, usually, studies for 5 hours. On some days, she may study for less number of hours and on the other days she may study longer.

Similarly, the average temperature of 40 degree celsius, means that, very often, the temperature at this time of the year is around 40 degree celsius. Sometimes, it may be less than 40 degree celsius and at other times, it may be more than 40°C.

Thus, we realise that average is a number that represents or shows the central tendency of a group of observations or data. Since average lies between the highest and the lowest value of the given data so, we say average is a measure of the central tendency of the group of data. Different forms of data need different forms of representative or central value to describe it. One of these representative values is the “Arithmetic Mean”. You will learn about the other representative values in the later of the chapter.

Please refer to attached file for NCERT Class 7 Maths Data Handling