NCERT Solutions for Class 11 Economics Chapter 2: Collection of Data
These Class 11 Economics Chapter 2 solutions cover Collection of Data from the NCERT textbook Statistics for Economics, updated for the 2026–27 session. The chapter explains the sources of data (primary and secondary), how data are collected through surveys and questionnaires, the difference between Census and Sample Surveys, the techniques of random and non-random sampling, the nature of sampling and non-sampling errors, and the important agencies of data collection in India (Census of India and NSSO). Below you get step-by-step answers to all 14 NCERT Exercises, key terms, extra practice, MCQs, Assertion–Reason questions and FAQs.
Class: 11Subject: EconomicsBook: Statistics for EconomicsChapter: 2Chapter Name: Collection of DataSession: 2026–27
Chapter 2, Collection of Data, deals with where economic data come from and how they are gathered. Data can be obtained from two sources — primary data, collected first-hand by the investigator through an enquiry or survey, and secondary data, which have already been collected and processed by some other agency. Data are commonly collected through surveys using a carefully framed questionnaire or interview schedule, administered through personal interviews, mailing questionnaires or telephone interviews, each with its own merits and demerits. The chapter distinguishes between a Census (complete enumeration of every unit of the population) and a Sample Survey (study of a representative part of the population), and explains random and non-random sampling. It also examines sampling errors (which fall as sample size rises) and the more serious non-sampling errors (sampling bias, non-response and errors in data acquisition), and ends with India’s key data agencies — the Census of India and the National Sample Survey (NSS/NSSO).
Key Concepts & Terms
Data: economic facts expressed in terms of numbers; a tool that helps in understanding a problem by providing information.
Primary data: data collected by the investigator first-hand through an enquiry or survey; they are original and based on first-hand information.
Secondary data: data that have already been collected and processed (scrutinised and tabulated) by some other agency, e.g. government reports, newspapers, books or websites. Use of secondary data saves time and cost.
Survey: a method of gathering information from individuals to describe characteristics such as price, quality, popularity or honesty.
Questionnaire / interview schedule: the most common instrument used in surveys; it should be short, simple, unambiguous, ordered from general to specific, and free of leading or double-negative questions.
Closed-ended (structured) questions: questions with fixed options — two-way (Yes/No) or multiple choice; easy to score but may miss the respondent’s true answer (hence the ‘Any Other’ option).
Open-ended (unstructured) questions: questions that allow individualised responses but are hard to interpret and score.
Census (complete enumeration): a survey that includes every element/unit of the population; in India it is carried out every ten years by the Registrar General.
Population (Universe): the totality of items under study — all individuals/items possessing a certain characteristic.
Sample: a representative group or section selected from the population, smaller than the population, that provides reasonably accurate information at lower cost and in less time.
Random sampling: sampling in which every unit of the population has an equal chance of being selected (the lottery method).
Non-random sampling: sampling in which units do not have an equal chance of selection; convenience, judgement, purpose or quota of the investigator decides the choice.
Sampling error: the difference between the sample estimate and the corresponding population parameter; it can be reduced by taking a larger sample.
Non-sampling errors: errors such as sampling bias, non-response errors and errors in data acquisition; they are more serious because they cannot be reduced merely by increasing sample size.
Important agencies: the Census of India (conducted every ten years, providing the most complete demographic record) and the National Sample Survey (NSS/NSSO), which conducts nation-wide socio-economic surveys in successive rounds.
NCERT “Exercises” — Full Solutions
All questions below are reproduced verbatim from the NCERT textbook’s end-of-chapter Exercises. Answers are original, written in exam-ready style.
1. Frame at least four appropriate multiple-choice options for following questions:
(i) Which of the following is the most important when you buy a new dress?(ii) How often do you use computers?(iii) Which of the newspapers do you read regularly?(iv) Rise in the price of petrol is justified.(v) What is the monthly income of your family?
ANSWER(i) Which of the following is the most important when you buy a new dress? (a) Price (b) Quality of cloth (c) Design/fashion (d) Brand name(ii) How often do you use computers? (a) Daily (b) Once or twice a week (c) Rarely (once a month or less) (d) Never(iii) Which of the newspapers do you read regularly? (a) The Times of India (b) The Hindu (c) Hindustan Times (d) Any other (please specify)(iv) Rise in the price of petrol is justified. (a) Strongly agree (b) Agree (c) Disagree (d) Strongly disagree(v) What is the monthly income of your family? (a) Less than ₹25,000 (b) ₹25,000–50,000 (c) ₹50,000–1,00,000 (d) More than ₹1,00,000
2. Frame five two-way questions (with ‘Yes’ or ‘No’).
ANSWERTwo-way questions are closed-ended questions that have only two possible answers, ‘Yes’ or ‘No’. Five such questions are:(i) Do you have a computer at home? (Yes / No)(ii) Is the electricity supply in your locality regular? (Yes / No)(iii) Do you read a newspaper every day? (Yes / No)(iv) Do you think smoking should be prohibited in public places? (Yes / No)(v) Do you save a part of your pocket money? (Yes / No)
3. State whether the following statements are True or False.
(i) There are many sources of data.(ii) Telephone survey is the most suitable method of collecting data, when the population is literate and spread over a large area.(iii) Data collected by investigator is called the secondary data.(iv) There is a certain bias involved in the non-random selection of samples.(v) Non-sampling errors can be minimised by taking large samples.
ANSWER(i) False. There are only two sources of data — primary sources and secondary sources.(ii) False. When the population is literate and spread over a large area, a mailing (questionnaire) survey is the most suitable, as it is the only economical method that can reach people in remote areas. (A telephone survey is limited because many people may not own telephones.)(iii) False. Data collected first-hand by the investigator are called primary data; data collected and processed by some other agency are secondary data.(iv) True. In non-random sampling, the convenience or judgement of the investigator decides which units are selected, so a certain bias is involved.(v) False. Only sampling errors can be reduced by taking a larger sample. Non-sampling errors are difficult to minimise even by increasing the sample size, and may even increase.
4. What do you think about the following questions? Do you find any problem with these questions? Describe.
(i) How far do you live from the closest market?(ii) If plastic bags are only 5 per cent of our garbage, should it be banned?(iii) Wouldn’t you be opposed to increase in price of petrol?(iv) Do you agree with the use of chemical fertilisers?(v) Do you use fertilisers in your fields?(vi) What is the yield per hectare in your field?
ANSWERYes, several of these questions have defects that a well-designed questionnaire should avoid:(i) The question is vague/ambiguous. “How far” can be answered in time or distance, and “closest market” is unclear. It should give clear options, e.g. “Less than 1 km / 1–2 km / more than 2 km.”(ii) This is a leading question. By stating “only 5 per cent”, it gives a clue and biases the respondent towards saying “No”. The figure should be removed.(iii) This uses a double negative (“Wouldn’t you be opposed”), which is confusing and leads to biased responses. It should be reframed simply, e.g. “Do you support the increase in the price of petrol?”(iv) This is ambiguous and presumptive — “agree with the use” is general; it does not specify the context (food crops, environment, etc.). It needs to be made precise.(v) This question is clear and acceptable; it is a simple two-way (Yes/No) question.(vi) This question is clear and acceptable; it asks for a specific, measurable fact (yield per hectare).
5. You want to do a research on the popularity of Vegetable Atta Noodles among children. Design a suitable questionnaire for collecting this information.
ANSWERA good questionnaire should move from general to specific, be short, clear and unambiguous, and use mostly closed-ended questions. A suitable questionnaire is:1. Name (optional): __________ Age: ______ Class: ______2. Do you eat noodles? (a) Yes (b) No3. Have you ever eaten Vegetable Atta Noodles? (a) Yes (b) No4. How often do you eat Vegetable Atta Noodles? (a) Daily (b) Once or twice a week (c) Once a month (d) Rarely5. What do you like most about Vegetable Atta Noodles? (a) Taste (b) Health/nutrition (c) Easy to cook (d) Any other (specify) ______6. Do you find Vegetable Atta Noodles healthier than ordinary noodles? (a) Yes (b) No (c) Can’t say7. Would you recommend Vegetable Atta Noodles to your friends? (a) Yes (b) No8. Any suggestions to improve the product? __________ (open-ended)
6. In a village of 200 farms, a study was conducted to find the cropping pattern. Out of the 50 farms surveyed, 50% grew only wheat. What is the population and the sample size?
ANSWERThe population is the totality of all the items under study. Here the study is about the cropping pattern of the farms in the village, so the population = all 200 farms in the village.The sample is the part of the population actually surveyed. Here 50 farms were surveyed, so the sample size = 50 farms.(The figure ‘50% grew only wheat’ describes a result of the survey, not the sample size. So population = 200 farms and sample size = 50 farms.)
7. Give two examples each of sample, population and variable.
ANSWERPopulation (two examples): (i) all the students of a school; (ii) all the agricultural labourers in a district.Sample (two examples): (i) 50 students selected from a school of 1,000 students; (ii) ten per cent of the agricultural labourers selected from a district for study.Variable (two examples): (i) the income of a person; (ii) the production of food grains in different years. (A variable is a characteristic that takes different values, generally represented by X, Y or Z.)
8. Which of the following methods give better results and why?
(a) Census (b) Sample
ANSWERIn general, the Census method gives more accurate and reliable results, because it covers every single unit of the population and so there is no sampling error.However, the Census method is very expensive, time-consuming and requires a large number of enumerators, so it is not always practical. Therefore, in most situations the Sample method is preferred — it provides reasonably reliable and accurate results at much lower cost and in less time, allows more detailed enquiry, and needs a smaller team that is easier to train and supervise.Thus, the choice depends on the purpose: the Census gives better (error-free) results when complete coverage is essential, while a well-drawn sample gives better practical results when resources are limited.
9. Which of the following errors is more serious and why?
(a) Sampling error (b) Non-Sampling error
ANSWERNon-sampling errors are more serious than sampling errors.A sampling error is the difference between the sample estimate and the actual population parameter; it can be reduced by taking a larger sample. A non-sampling error, however, arises from sampling bias, non-response or mistakes in data acquisition, and it is difficult to minimise even by taking a larger sample — in fact, even a complete Census can contain non-sampling errors. Because they cannot be controlled simply by increasing the sample size, non-sampling errors are regarded as more serious.
10. Suppose there are 10 students in your class. You want to select three out of them. How many samples are possible?
ANSWERThe number of possible samples of size 3 chosen from 10 students is given by the combination formula nCr, where n = 10 and r = 3 (the order of selection does not matter).
Therefore, 120 different samples of 3 students each are possible.
11. Discuss how you would use the lottery method to select 3 students out of 10 in your class.
ANSWERThe lottery method is a simple way of drawing a random sample in which every unit has an equal chance of selection. To select 3 students out of 10:Step 1: Write the names (or roll numbers) of all 10 students on 10 identical slips of paper.Step 2: Fold the slips in the same way so that none can be identified, and put them into a box or bowl.Step 3: Mix the slips thoroughly so that they are well shuffled.Step 4: Without looking, draw one slip at a time. Repeat until 3 slips have been drawn.The 3 students whose names appear on the drawn slips form the random sample. Since each slip is identical and mixing is thorough, every student has an equal chance of being selected.
12. Does the lottery method always give you a random sample? Explain.
ANSWERThe lottery method gives a random sample only if it is carried out properly — that is, if all the slips are identical in size, shape and folding, and if they are mixed thoroughly before each draw so that every unit truly has an equal chance of selection.If these conditions are not met — for example, if some slips are larger or folded differently, or the slips are not mixed well — then certain slips are more likely to be picked, every unit no longer has an equal chance, and the sample drawn is not truly random. So the lottery method does not always give a random sample; it does so only when applied carefully and fairly.
13. Explain the procedure for selecting a random sample of 3 students out of 10 in your class by using random number tables.
ANSWERA random number table is a published table of digits arranged in a random order, used to select a sample without bias. To select 3 students out of 10:Step 1: Number the 10 students from 00 to 09 (or 01 to 10), so that each has a unique two-digit code.Step 2: Choose any starting point in the random number table and decide a direction (read row-wise or column-wise) in advance.Step 3: Read off two-digit numbers one after another. Select a student whenever the number read corresponds to one of the codes 00–09.Step 4: Ignore numbers that do not fall in this range, and ignore any number that has already been selected (to avoid repetition), until 3 valid numbers have been obtained.The 3 students corresponding to these numbers form the random sample. This method removes personal bias because the choice is decided entirely by the table.
14. Do samples provide better results than surveys? Give reasons for your answer.
ANSWERThe question compares a sample survey with a complete survey (census). In most practical situations, a well-drawn sample provides better (more workable) results than a complete census survey, for the following reasons:(i) Lower cost: a sample studies only a part of the population, so it is far cheaper than surveying everyone.(ii) Less time: data from a smaller group can be collected and processed much faster.(iii) More detailed information: as samples are smaller, intensive and detailed enquiries can be made for each unit.(iv) Easier organisation: a smaller team of enumerators is needed, so they can be trained better and supervised more effectively, reducing non-sampling errors.However, a sample is reliable only if it is representative; if accuracy and complete coverage are essential (as in a population Census), a complete survey gives better, error-free results. So samples give better practical results when resources are limited and the sample is representative.
Extra Practice Questions
Short Answer Type Questions
Q1. Distinguish between primary and secondary data.
ANSWERPrimary data are collected first-hand by the investigator through an enquiry or survey and are original (based on first-hand information). Secondary data have already been collected and processed by some other agency and are obtained from published sources such as reports, newspapers, books or websites. Data are primary to the source that collects them first and secondary for all who use them later.
Q2. What is a pilot survey? Why is it useful?
ANSWERA pilot survey (or pre-testing of the questionnaire) is a try-out of the questionnaire on a small group before the actual survey. It is useful because it reveals the shortcomings and drawbacks of the questions, checks the clarity of instructions and the suitability of questions, assesses the performance of enumerators, and gives an idea of the cost and time the actual survey will involve.
Q3. State any three points to be kept in mind while preparing a questionnaire.
ANSWER(i) The questionnaire should not be too long; the number of questions should be the minimum needed. (ii) Questions should be precise, clear, easy to understand and free from ambiguous or difficult words. (iii) Questions should move from general to specific, and should avoid leading questions, double negatives and questions that suggest the answer.
Q4. Define population and sample.
ANSWERA population (or universe) is the totality of all the items under study — all the individuals or units that possess a certain characteristic, to which the results of the study are intended to apply. A sample is a group or section selected from the population from which information is actually obtained; a good (representative) sample is smaller than the population yet gives reasonably accurate information at lower cost.
Q5. What are the three basic methods of collecting data through surveys?
ANSWERThe three basic ways of collecting data are: (i) Personal Interviews, where the investigator conducts face-to-face interviews; (ii) Mailing (questionnaire) Surveys, where the questionnaire is sent and returned by mail; and (iii) Telephone Interviews, where the investigator asks questions over the telephone.
Long Answer Type Questions
Q1. Explain the merits and demerits of personal interviews, mailing surveys and telephone interviews.
ANSWERPersonal interview: Merits — it has the highest response rate, allows all types of questions (especially open-ended ones), permits clarification of ambiguous questions, and lets the interviewer watch the respondent’s reactions. Demerits — it is the most expensive method, time-consuming, and the interviewer’s presence may influence respondents. Mailing survey: Merits — least expensive, the only method that can reach remote areas, free from interviewer influence, maintains anonymity and is best for sensitive questions. Demerits — it cannot be used by illiterates, has a long response time and low response rate, does not allow explanation of unclear questions, and reactions cannot be watched. Telephone interview: Merits — relatively low cost, can be done quickly, allows the researcher to clarify questions, relatively less influence and good for reluctant respondents. Demerits — limited use because many people may not own telephones, reactions cannot be watched, and there is a possibility of influencing respondents.
Q2. Distinguish between Census and Sample Survey, and explain why sample surveys are usually preferred.
ANSWERA Census, or the method of complete enumeration, includes every element of the population — for example, the Census of India covers every household in the country and is conducted every ten years. A Sample Survey studies only a representative part (sample) of the population and uses its results to estimate the characteristics of the whole population. The Census is more accurate (no sampling error) but is very costly, time-consuming and needs a huge team of enumerators. Sample surveys are usually preferred because: (i) they provide reasonably reliable and accurate information at a much lower cost; (ii) they save time; (iii) being smaller, they allow more detailed and intensive enquiry; and (iv) a smaller team of enumerators is easier to train and supervise, which also helps control non-sampling errors. Hence most surveys in statistics are sample surveys, while a Census is reserved for cases where complete coverage is essential.
Q3. Describe the different types of non-sampling errors.
ANSWERNon-sampling errors are errors that arise from causes other than sampling, and they are more serious because they cannot be reduced just by enlarging the sample — even a Census can contain them. The main types are: (i) Sampling bias — this occurs when the sampling plan is such that some members of the target population can never be included in the sample, so the sample is not representative. (ii) Non-response errors — these arise when an interviewer cannot contact a person listed in the sample, or when a selected person refuses to respond, leaving the observations unrepresentative. (iii) Errors in data acquisition — these arise from recording incorrect responses, for example differences in measuring instruments, carelessness, or transcription mistakes such as recording 13 instead of 31. Careful planning, training of enumerators and verification help reduce these errors.
MCQs & Assertion–Reason
1. Data collected first-hand by the investigator are called:
(a) secondary data (b) primary data (c) published data (d) processed data
2. A survey that includes every element of the population is called:
(a) sample survey (b) pilot survey (c) census (d) random survey
3. The most common instrument used in a survey is the:
(a) calculator (b) random number table (c) questionnaire (d) graph
4. In random sampling, every unit of the population:
(a) is excluded (b) has an equal chance of being selected (c) is chosen by judgement (d) is chosen for convenience
For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.
A-R 1. Assertion: Secondary data save time and cost.
Reason: Secondary data have already been collected and processed by some other agency.
A-R 2. Assertion: Sampling errors can be reduced by taking a larger sample.
Reason: A sampling error is the difference between the sample estimate and the population parameter.
A-R 3. Assertion: Non-sampling errors are less serious than sampling errors.
Reason: Non-sampling errors can be eliminated completely by conducting a Census.
A-R 4. Assertion: A mailing questionnaire is suitable for reaching people in remote areas.
Reason: The mailing method is the least expensive method and does not allow the interviewer to influence respondents.
A-R 5. Assertion: In non-random sampling, every unit does not have an equal chance of selection.
Reason: In non-random sampling, the convenience or judgement of the investigator decides the selection of units.
Answer key: 1-(A), 2-(B), 3-(D), 4-(B), 5-(A).
Exam Tips & Common Mistakes
How to score full marks in this chapter
Learn the clear distinctions in this chapter as point-wise comparisons: primary vs secondary data, Census vs Sample survey, random vs non-random sampling, and sampling vs non-sampling errors. Remember the three methods of data collection with their merits and demerits (use the textbook’s advantages/disadvantages table). For the combination problem (Q10), use nCr and always show the working — 10C3 = 120. When asked to spot problems in questions, name the exact defect (leading, double-negative, ambiguous, etc.). Quote real Indian agencies — Census of India (every 10 years) and the NSS/NSSO — to show thorough study.
Common mistakes to avoid
Calling data collected by the investigator “secondary” — first-hand data are primary.
Writing that “non-sampling errors can be reduced by a larger sample” — only sampling errors fall as sample size rises.
Confusing the result of a survey with the sample size (Q6: sample = 50 farms, not 25).
Forgetting that combinations (not permutations) are used to count samples — order does not matter.
Saying there are “many sources of data” — there are only two: primary and secondary.
Mixing up open-ended (free response) and closed-ended (fixed options) questions.
Frequently Asked Questions
What is Chapter 2 of Class 11 Economics (Statistics for Economics) about?
Chapter 2, Collection of Data, explains the sources of data (primary and secondary), how data are collected through surveys and questionnaires, the difference between Census and Sample Surveys, random and non-random sampling, sampling and non-sampling errors, and India’s key data agencies — the Census of India and the National Sample Survey (NSSO).
What is the difference between primary and secondary data?
Primary data are collected first-hand by the investigator through an enquiry or survey and are original. Secondary data have already been collected and processed by some other agency and are obtained from published sources such as government reports, newspapers, books or websites. Using secondary data saves time and cost.
How many questions are in the NCERT exercise of Chapter 2 Collection of Data?
The end-of-chapter Exercises of Statistics for Economics Chapter 2 has 14 numbered questions, including question-framing tasks, True/False, a combinations problem and theory questions — all answered step by step on this page.
