Quick Revision Notes: Economics (Class 11)

Chapter: Collection of Data

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Introduction

• Data (आँकड़े): Facts and figures collected for a specific purpose to help in understanding a phenomenon or making decisions.
• Statistician (सांख्यिकीविद्): A person who collects, analyzes, interprets, and presents quantitative data.

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Concept 1: Sources of Data

Data can be collected from two primary sources:

1. Primary Data (प्राथमिक आँकड़े):

   • Definition: Data collected for the first time by the investigator for their own specific purpose. It is original in character.
   • Features: First-hand information, reliable, specific to the problem, but time-consuming and expensive.

2. Secondary Data (द्वितीयक आँकड़े):

   • Definition: Data that has already been collected and published/processed by someone else (e.g., government reports, books, journals).
   • Features: Already available, less expensive, quick, but may not be entirely relevant or reliable for the current study.

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Concept 2: Methods of Collecting Primary Data

An investigator can collect primary data through the following methods:

1. Direct Personal Investigation (प्रत्यक्ष व्यक्तिगत अनुसंधान):

   • Investigator collects data personally by establishing direct contact with the informants.
   • Suitability: Original data required, intensive study, secret information.

2. Indirect Oral Investigation (अप्रत्यक्ष मौखिक अनुसंधान):

   • Information is collected through third parties (witnesses) who are closely associated with the problem.
   • Suitability: Wide area of study, informants are not accessible directly, complex matters.

3. Information through Correspondents (संवाददाताओं द्वारा सूचना):

   • Local agents or correspondents are appointed in different places to collect information.
   • Suitability: Continuous information needed (e.g., news reporting), large area.

4. Mail Questionnaire Survey (डाक द्वारा प्रश्नावली):

   • Questionnaires are sent to informants by post along with a self-addressed stamped envelope.
   • Suitability: Educated informants, large and scattered geographical area.

5. Enumerator Survey (प्रगणक सर्वेक्षण / टेलीफोनिक साक्षात्कार):

   • Enumerators themselves go to informants, ask questions, and fill out the schedules. Often done via interviews or telephone.

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Concept 3: Essentials of a Good Questionnaire (प्रश्नावली की विशेषताएँ)

A questionnaire is a set of questions related to the study. A good questionnaire must have:

• Limited number of questions (not too lengthy).
• Simple, clear, and unambiguous questions.
• Proper sequence of questions (easy to difficult).
• No personal or sensitive questions that hurt sentiments.
• Multiple-choice or closed-ended questions preferably (Yes/No, multiple options).

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Concept 4: Sources of Secondary Data

Secondary data is classified into two types based on its origin:

1. Published Sources (प्रकाशित स्रोत):

   • Government Publications (e.g., Census of India, Reserve Bank of India Reports).
   • Semi-Government Publications (e.g., Municipal Corporation reports).
   • Reports of Committees and Commissions.
   • Publications of Trade Associations, Research Institutions, and Newspapers.

2. Unpublished Sources (अप्रकाशित स्रोत):

   • Data collected by private organizations, individuals, or researchers that are not formally published.

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Concept 5: Census vs. Sample Survey (जनगणना बनाम प्रतिदर्श सर्वेक्षण)

Feature	Census Method (जनगणना विधि)	Sample Survey Method (प्रतिदर्श सर्वेक्षण विधि)
Meaning	Data is collected from every single unit of the population.	Data is collected from a representative sample of the population.
Accuracy	High degree of accuracy.	Possibility of sampling errors, but generally reliable.
Time & Cost	Highly expensive and time-consuming.	Economical in terms of time, money, and labor.
Suitability	When units have diverse characteristics and population size is small.	When population size is large and uniform.

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Concept 6: Sampling Methods (प्रतिचयन की विधियाँ)

Under the sample survey method, samples are selected using various techniques:

1. Random Sampling (यादृच्छिक प्रतिचयन):
   • Every unit of the population has an equal and independent chance of being selected (Lottery method, Random number tables).
2. Purposive / Deliberate Sampling (उद्देश्यपूर्ण प्रतिचयन):
   • The investigator intentionally selects the sample units based on their own judgment or purpose.
3. Stratified / Mixed Sampling (स्तरीकृत प्रतिचयन):
   • The population is divided into different homogenous groups (strata), and samples are drawn from each group.
4. Systematic Sampling (व्यवस्थित प्रतिचयन):
   • Every $n^{th}$ item of the population is selected after arranging them in some order.
5. Quota Sampling (कोटा प्रतिचयन):
   • Quotas are fixed for different segments of the population, and investigators choose units to fill those quotas.

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Concept 7: Errors in Data Collection (आँकड़ों में त्रुटियाँ)

1. Sampling Errors (प्रतिचयन त्रुटियाँ): Errors that occur because data is collected from a sample instead of the entire population. (Can be minimized by increasing sample size).
2. Non-Sampling Errors (गैर-प्रतिचयन त्रुटियाँ): More serious errors that occur during data collection, such as errors in recording, faulty questionnaires, or biased responses from informants.

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Note for MP Board Students: Revise the differences between Primary & Secondary Data and Census & Sample methods thoroughly, as direct conceptual questions frequently appear in the exams.