Summary
Highlights
The video marks day eight of the '15 Days Pledge,' focusing on Chapter 2 of Statistics for Class 11: Collection of Data. It begins by defining data as comparable information leading to conclusions. It introduces two primary sources of data collection: primary and secondary. The person collecting data is termed an 'investigator'.
Primary data is collected directly by the investigator from the source of origin, offering first-hand, original information. An example given is an investigator directly collecting accident data by visiting accident sites. Secondary data, on the other hand, is pre-existing data collected by another agency or institution for a different purpose and is simply adopted by the investigator. An example is an investigator taking accident data from newspapers or the internet. Primary data is original and purpose-specific, while secondary data is not original and may require adjustments to fit the investigator's objective.
The video outlines three methods for collecting primary data: personal interviews, information through questionnaires and schedules, and telephone interviews. Personal interviews include Direct Personal Investigation (DPI), Indirect Oral Investigation (IOI), and Information from Local Sources and Correspondents (ILSC).
DPI involves the investigator directly collecting information from 'respondents' through personal contact. This method is suitable for limited investigation areas, when high originality, secrecy, and accuracy are required, and when direct contact is necessary. Its advantages are originality, accuracy, reliability, related information, uniformity, and elasticity. Disadvantages include limited coverage, potential for personal bias, and high cost.
IOI involves the investigator collecting information from a 'witness' who is expected to have the necessary information, rather than directly from the respondent. This method is suitable for large investigation areas, when direct contact with respondents is not possible, or when respondents are illiterate, ignorant, or the investigation requires expert opinions. Advantages include wider coverage, lower cost, expert opinions, relative impartiality of the investigator, and simplicity. Disadvantages are less accuracy, potential for witness bias, and the risk of careless replies.
ILSC involves the investigator appointing local people or correspondents to collect and supply information regularly. This method is suitable for continuous information requirements, large investigation areas (e.g., news channels), and when high accuracy is not paramount. Its benefits are being economical, offering wide coverage, providing continuous data, and suitability for specific purposes. Drawbacks include lack of originality, non-uniformity, potential for personal bias, less accuracy, and delays in collection.
This method involves the investigator preparing a questionnaire. There are two ways: Mail Survey (or Questionnaire Survey) and Enumeration Method.
In a mail survey, the investigator mails the questionnaire directly to respondents, who fill it out and return it. This is suitable for wide studies and when respondents are educated. It is economical, original, and allows wide coverage. However, it suffers from non-response, inflexibility, limited applicability to educated respondents, and potential for biased, less accurate, or incomplete answers.
The enumeration method involves the investigator hiring 'enumerators' who visit respondents, ask questions from the questionnaire (referred to as 'schedules'), and fill out the answers themselves. Enumerators receive special training. This method is suitable for large investigation areas and when specialized enumerators are available and familiar with local languages and culture. It offers wide coverage, allows data collection from illiterates, provides accurate information due to trained personnel and personal contact, ensures impartiality, and completeness. The disadvantages are high cost, dependency on the availability of competent enumerators, and it is time-consuming.
A good questionnaire should have a limited number of relevant, simple, and clear questions arranged in proper order. It should avoid undesirable, controversial, or mathematical questions. It benefits from pre-testing, clear instructions, cross-verification questions, and a polite request for return. Questions can be simple alternative (yes/no), multiple-choice, specific information, or open-ended.
Telephone interviews involve the investigator collecting information from respondents over the phone. Its advantages include original and accurate information, reliability, low cost, and absence of personal embarrassment for respondents. Disadvantages include potential for personal bias from respondents, investigator bias, and limited access to only those with telephones.
Secondary data sources are divided into Published Sources and Unpublished Sources. Published sources include Government Publications (Central and State), Semi-Government Publications (Municipalities), Reports of Committees and Commissions (e.g., NITI Aayog), Trade Associations (e.g., sugar mills), Research Institutions, Newspapers, Journals, Research Scholars, and International Publications (e.g., UNO, IMF, World Bank). Unpublished sources are data collected by government institutions for their internal use, not publicly released.
When using secondary data, it is crucial to consider: the ability of the original collecting organization, the objective for which the data was initially collected, the method of collection used, the time period of collection, the definitions of units used, and the accuracy of the data. Mismatches in any of these aspects can lead to incorrect conclusions.
Two major sources of secondary data in India are the Census of India and reports from the National Sample Survey Office (NSSO). The Census of India is a decennial publication (every 10 years) by the Registrar General and Census Commissioner, providing comprehensive population data. NSSO reports, published by a government organization under the Ministry of Statistics and Program Implementation, gather sample-based information on various socio-economic aspects like land and livestock holdings, housing conditions, migration, employment, consumer expenditure, and household income.