What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

What is a variable and an observation?

A variable is a quantity that varies, such as food-grain output across years (denoted X, Y or Z), and each individual value the variable takes is an observation.

What points should a good questionnaire follow?

It should be short, use clear and unambiguous words, avoid double negatives and leading questions, not suggest alternatives, and arrange questions from general to specific.

Distinguish between closed-ended and open-ended questions.

Closed-ended (structured) questions offer fixed options — two-way (yes/no) or multiple-choice — and are easy to score; open-ended questions allow free individual responses but are hard to interpret.

Name the three modes of collecting data and a merit of each.

Personal interview (highest response rate), mailed questionnaire (least expensive, reaches remote areas) and telephone interview (cheaper and quicker than personal interview).

What is the purpose of a pilot survey?

A pilot survey or pre-test tries the questionnaire on a small group to reveal shortcomings, assess clarity of instructions, performance of enumerators and the cost and time involved.

Distinguish between census and sample survey.

A census enumerates every unit of the population, while a sample survey studies only a representative part, providing reasonably accurate results at lower cost and in less time.

What is random sampling?

A method in which every unit of the population has an equal chance of being selected, for example by the lottery method or random number tables, so the sample is unbiased.

Define sampling error and state how it can be reduced.

It is the difference between a sample estimate and the true population value; it can be reduced by taking a larger sample.

Why are non-sampling errors more serious than sampling errors?

Because they arise from bias, non-response or wrong recording (such as writing 13 for 31) and cannot be minimised simply by enlarging the sample; they can occur even in a census.

Collection of Data

Q: Distinguish between primary and secondary data.

Primary data are collected first-hand by the investigator through an enquiry, while secondary data have already been collected and processed by another agency and are reused; the same data are primary to their first collector and secondary to all later users.

Class 11 Economics · Statistics for Economics · Chapter 2

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Summary

After knowing why data matter, the next step is to collect them, since data help understand a problem by providing evidence. A quantity that varies, like food-grain output across years, is a variable (denoted X, Y or Z), and each value is an observation. Data come from two sources: primary data are gathered first-hand through an enquiry, while secondary data have already been collected and processed by another agency and reused from reports, books, newspapers or websites; the same figures are primary to the body that first compiles them and secondary to all who borrow them later. A survey gathers information through a questionnaire whose questions should be short, clear and unambiguous, avoid double negatives and leading phrasing, and move from general to specific. Data can be collected by personal interview, mailed questionnaire or telephone interview, differing in cost, response rate and reach; a pilot survey pre-tests the questionnaire first. A survey may cover every unit (a census or complete enumeration, done in India every ten years) or only a representative sample, which is cheaper. Samples are chosen by random methods, where every unit has an equal chance, or non-random methods relying on judgement. Errors are of two kinds: sampling errors, the gap between a sample estimate and the true value, which shrink with larger samples, and non-sampling errors from bias, non-response or faulty recording. The Census of India and the National Sample Survey are key agencies.

Collection of Data

Key terms

Primary data

Data collected first-hand by the investigator through an original enquiry or survey.

Secondary data

Data already collected and processed by another agency and reused by the investigator.

Census

A survey that covers every unit of the population; complete enumeration, done in India every ten years.

Sample

A representative section of the population from which information is gathered at lower cost and time.

Sampling error

The difference between a sample estimate and the corresponding true population value.

Pilot survey

A small try-out of the questionnaire before the main survey, to pre-test it for shortcomings.

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Data collected first-hand by the investigator are called:

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Collection of Data

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