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Organisation of Data – Class 11 Economics notes, important questions and MCQs

NCERT Class 11 Economics, chapter 3. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Raw data collected in a survey are unorganised and difficult to understand. Classification arranges data into groups with common characteristics. Data can be classified chronologically, spatially, qualitatively or quantitatively. A frequency distribution shows how often values occur in each class and is the basic tool for further analysis.

Classification

Chronological classification groups data by time, such as population by year.
Spatial classification groups data by place, such as wheat output by state.
Qualitative classification groups by attributes, such as gender or literacy; quantitative classification groups by measurable values, such as marks or income.

Variables

A variable is a characteristic that can take different values.
A discrete variable takes only certain values, usually whole numbers, such as the number of children.
A continuous variable can take any value within a range, such as height or weight.

Frequency distribution

A frequency distribution shows the number of observations (frequency) in each class; tally marks help in counting.
Class limits are the lowest and highest values of a class; class interval (width) = upper limit − lower limit.
Class mark (mid-value) = (upper limit + lower limit) ÷ 2.
In the exclusive method (10–20, 20–30) the upper limit is excluded; in the inclusive method (10–19, 20–29) both limits are included.

Key terms

Classification: arranging data into groups or classes according to common characteristics
Frequency: the number of times a value or class occurs in a data set
Class interval: the difference between the upper and lower limits of a class
Class mark: the mid-value of a class, found by (upper limit + lower limit) ÷ 2
Continuous variable: a variable that can take any value within a given range

Important questions with answers

What is the difference between discrete and continuous variables?2 marks

A discrete variable can take only certain separate values, usually whole numbers, such as the number of students in a class. A continuous variable can take any value within a range, including fractions, such as height, weight or temperature.

Explain the exclusive and inclusive methods of forming classes.3 marks

In the exclusive method, the upper limit of one class is the lower limit of the next, as in 10–20, 20–30, and an item equal to the upper limit is placed in the next class. In the inclusive method, both limits are included in the class, as in 10–19, 20–29, so there is a gap between classes. The exclusive method is suitable for continuous data and the inclusive method for discrete data.

What is classification? Explain its types and the construction of a frequency distribution.5 marks

Classification is the process of arranging raw data into groups or classes on the basis of common characteristics, so that the data become brief, clear and comparable. Data can be classified in four ways. Chronological classification groups data by time, for example India's population in different census years. Spatial classification groups data by place, for example rice production in different states. Qualitative classification groups data by attributes such as gender, religion or literacy. Quantitative classification groups data by measurable characteristics such as marks, income or height. A frequency distribution is a common form of quantitative classification. To construct it, first find the range of the data and decide the number of classes and the class interval. Then write the classes, using the exclusive or inclusive method, go through the raw data and mark a tally for each observation against its class, and count the tallies to obtain the frequency of each class. The class mark of each class is (upper limit + lower limit) ÷ 2. The total of frequencies must equal the number of observations. A frequency distribution condenses data and forms the basis of graphs and averages.

Quick revision

Chronological, spatial, qualitative, quantitative.
Discrete vs continuous variables.
Class interval = upper − lower limit.
Class mark = (upper + lower) ÷ 2.

Exam tips

Practise one frequency table with tally marks from raw marks.
Remember the class mark formula and the exclusive vs inclusive difference.

Practice MCQs

Grouping data by year is
1. spatial classification
2. qualitative classification
3. chronological classification
4. random classification
Show answer
Answer: (c) chronological classification. It is based on time.
The number of times a value occurs is its
1. class mark
2. frequency
3. range
4. limit
Show answer
Answer: (b) frequency. Tally marks help to count it.
The number of children in a family is a
1. discrete variable
2. continuous variable
3. qualitative attribute
4. class limit
Show answer
Answer: (a) discrete variable. It takes whole-number values.
The class mark of the class 20–30 is
1. 20
2. 25
3. 30
4. 50
Show answer
Answer: (b) 25. (20 + 30) ÷ 2 = 25.
In the class 40–50, the class interval is
1. 10
2. 50
3. 40
4. 90
Show answer
Answer: (a) 10. 50 − 40 = 10.
Classification of students as literate or illiterate is
1. qualitative
2. quantitative
3. chronological
4. spatial
Show answer
Answer: (a) qualitative. It is based on an attribute.
In exclusive classes 10–20 and 20–30, a value of 20 is placed in
1. 10–20
2. neither class
3. both classes
4. 20–30
Show answer
Answer: (d) 20–30. The upper limit is excluded from its class.
Which of these is a continuous variable
1. number of cars
2. number of books
3. number of rooms
4. height of students
Show answer
Answer: (d) height of students. Height can take fractional values.

All chapters of Class 11 Economics

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.