Collection of Data

• Introduction
  • Meaning of Data
  • Role of data in Economics
  • Objectives of data collection
• Sources of Data
  • Primary Data
    • Meaning: First-hand information
    • Original and specific to the problem
  • Secondary Data
    • Meaning: Pre-collected data
    • Collected by someone else for another purpose
• Methods of Collecting Primary Data
  • Direct Personal Investigation
    • Face-to-face contact with informants
    • High accuracy, costly, time-consuming
  • Indirect Oral Investigation
    • Collecting data through third parties (witnesses)
    • Used when direct contact is not possible
  • Information through Local Sources/Correspondents
    • Appointing local agents in different areas
    • Quick, but lacks high degree of accuracy
  • Mailed Questionnaire Method
    • Questionnaires sent via post
    • Wide coverage, but low response rate
  • Enumerators Schedule Method
    • Enumerators fill questionnaires themselves
    • Highly reliable, requires trained staff
• Designing a Questionnaire
  • Meaning of a Questionnaire
  • Qualities of a good questionnaire
    • Limited number of questions
    • Simple and clear language
    • Proper sequence of questions
    • Avoid personal or controversial questions
    • Inclusion of cross-check questions
  • Pre-testing (Pilot Survey)
• Sources of Secondary Data
  • Published Sources
    • Government publications (e.g., Census of India)
    • Semi-government publications
    • Reports of committees and commissions
    • Publications of research institutions
    • International publications (e.g., IMF, World Bank)
    • Newspapers and magazines
  • Unpublished Sources
    • Census data not yet published
    • Private research records
• Precautions in Using Secondary Data
  • Reliability of the data
  • Suitability for the present study
  • Adequacy of the data
• Census and Sample Surveys
  • Census Method
    • Complete enumeration of every unit
    • High accuracy, expensive, time-consuming
  • Sample Method
    • Enumeration of a representative part (sample)
    • Economical, less time-consuming, margin of error
  • Essential of a Good Sample
    • Representativeness
    • Independence
    • Homogeneity
    • Adequacy of size
• Methods of Sampling
  • Random Sampling (Probability Sampling)
    • Every unit has an equal chance of selection
    • Lottery method, Random number tables
  • Non-Random Sampling (Non-Probability Sampling)
    • Purposive (Judgment) Sampling: Selected based on investigator's judgment
    • Quota Sampling: Selection based on fixed quotas or categories
    • Stratified Sampling: Population divided into strata, then sampled
• Sampling Errors and Non-Sampling Errors
  • Sampling Errors
    • Difference between sample estimate and actual population parameter
    • Can be reduced by increasing sample size
  • Non-Sampling Errors
    • Errors in data acquisition (bias, non-response, calculation errors)
    • More serious than sampling errors