What are the Sources of Data?

Sources of Data

The sources of data can be classified into two types: statistical and non-statistical. Statistical sources refer to data that is gathered for some official purposes, incorporate censuses, and officially administered surveys. Non-statistical sources refer to the collection of data for other administrative purposes or for the private sector.

What are the different sources of data?

The following are the two sources of data:

  1. Internal sources
  • When data is collected from reports and records of the organisation itself, they are known as the internal sources.
  • For example, a company publishes its annual report’ on profit and loss, total sales, loans, wages, etc.
  1. External sources
  • When data is collected from sources outside the organisation, they are known as the external sources. For example, if a tour and travel company obtains information on Karnataka tourism from Karnataka Transport Corporation, it would be known as an external source of data.

Types of Data

A) Primary data

  • Primary data means first-hand information collected by an investigator.
  • It is collected for the first time.
  • It is original and more reliable.
  • For example, the population census conducted by the government of India after every ten years is primary data.

B) Secondary data

  • Secondary data refers to second-hand information.
  • It is not originally collected and rather obtained from already published or unpublished sources.
  • For example, the address of a person taken from the telephone directory or the phone number of a company taken from Just Dial are secondary data.

Students can also refer to Meaning and Sources of Secondary Data

Methods of Collecting Primary Data

  1. Direct personal investigation
  2. Indirect oral investigation
  3. Information through correspondents
  4. Telephonic interview
  5. Mailed questionnaire
  6. The questionnaire filled by enumerators
1. Give the meaning of the following terms:

(A) Investigator

(B) Enumerator

(C) Informant/Respondent

Investigator     One who conducts investigation, i.e., statistical enquiry and seeks information is known as an investigator.

    It can be an individual person or an organisation.

Enumerator     An enumerator is a person who helps investigators in the collection of data.
Informant     An informant is the respondent who supplies the information to the investigators or enumerators.

Direct Personal Investigation

Q.1 Explain direct personal investigation method of collecting primary data. Discuss its merits and demerits.
(A) Direct personal investigation     Under this method, the investigator obtains the first-hand information from the respondents themselves.

    He personally visits the respondents to collect the information (data).

(B) Following are the merits of direct personal investigation:
(1) Reliable and Accurate     The data collected is first-hand and original in nature. So, it is more reliable and accurate.
(2) Flexibility     In this method, the questions can be modified according to the level of the respondent or other situations.
(3) Additional information     Some additional information may also be collected along with the required information.

    This additional information can be used in future investigations.

(C) Following are the demerits of direct personal investigation:
(1) Not suitable for a wide area     It is not suitable when the area of coverage is considerably wide.
(2) Time-consuming     This method is time-consuming as the investigator personally visits various places and meets different people to collect information.
(3) Expensive     This method is expensive, particularly when the field of investigation is large.
(4) Personal bias     The data collected in this method is subjected to personal bias.

Indirect Oral Investigation

Q.1 Explain indirect oral investigation method of collecting primary data. Give its merit and demerits.
(A) Indirect oral investigation Under this method, instead of directly approaching the informants, the investigators interview several other persons who are directly or indirectly in touch with the informants.
(B) Following are the merits of indirect oral investigation:
(1) Wide coverage     A wide area can be brought under investigation through this method.
(2) Economical     It is economical in terms of time, money, and manpower.
(C) Following are the demerits of indirect oral investigation:
(1) Indirect information     Since the information is not collected directly from the party, there is a possibility that it will not be fully true.
(2) Lack of accuracy     As compared to direct personal investigation, the degree of accuracy of the data is likely to be lower.
(3) Lack of uniformity     Information collected from different persons for the same party may not be homogeneous and comparable.
(4) Possibility of biased information     Respondent/witness can modify the information according to his personal interest.


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Information through Correspondents

Q.1 Explain information through correspondents’ method of collecting primary data. Give its merit and demerits.
(A) Information through correspondents Under this method, local agents or correspondents are appointed and trained to collect the information from the respondents.
(B) Following are the merits of information through correspondents:
(1) Wide coverage     This method is useful where the field of investigation is very wide and the information is to be collected from different parts of the country.
(2) Economical     This method is quite economical and time-saving.
(3) Suitable for special purposes     This method is suitable for some special purpose investigations.
(4) Continuity     It is very useful for collecting information on a regular basis.
(C) Following are the demerits of information through correspondents:
(1) Lack of uniformity     The information supplied by different correspondents often lacks homogeneity; hence it is not comparable.
(2) Lack of reliability     Data obtained using this method may not be very reliable because of the possibility of personal bias and prejudice of the enumerator.
(3) Less accuracy     This method cannot be used where a high degree of accuracy is required.
(4) Costly     A lot of time and money is spent to collect the information through correspondence.


Telephonic interviews

Q.1 Explain the telephonic interviews method of collecting primary data. Give its merit and demerits.
(A) Telephonic interviews Under this method, data is collected through interviews over the telephone.
(B) Following are the merits of telephonic interviews:
(1) Wide coverage ●     This method is useful where the field of investigation is very wide and the information is to be collected from different parts of the country.
(2) Economical ●     This method is quite economical and time-saving.
(3) Reliability ●     The collected data is reliable as it is obtained directly from the party.
(C) Following are the demerits of telephonic interviews:
(1) Limited use ●     The disadvantage of this method is limited accessibility to people. This method is not possible for people who do not own a telephone or mobile.
(2) Visual feedback is not possible ●     Telephone interviews also obstruct visual reactions of the respondents, which become helpful in obtaining information on sensitive issues.

Mailed Questionnaire Method

Q.1 Discuss the mailed questionnaire method of collecting primary data. What are its merits and demerits?
(A) Mailed questionnaire method ●     Under this method, a questionnaire containing a number of questions related to the investigation is prepared.

●     It is then sent to informants by post along with the instructions to fill.

●     The informants, after filling up the questionnaire, send it back to the investigator.

(B) Following are the merits of the mailed questionnaire method:
(1) Wide coverage ●     This method is useful where the field of investigation is very wide and the information is to be collected from different parts of the country.
(2) Economical ●     This method is quite economical as it requires less money and labour.
(3) Originality ●     The data is very much original because informants are directly involved in the collection of data.
(4) Free from bias ●     Every question is interpreted by the respondent in his own way. Hence, it is free from the personal bias of the investigator.
(5) Maintains secrecy ●     This method is suitable for sensitive questions and maintains the anonymity of respondents.
(C) Following are the demerits of the mailed questionnaire method:
(1) Limited scope ●     This method is applicable only where the respondents are educated.
(2) Less response ●     Most informants do not return the questionnaire.

●     The informants are least interested in the investigation; hence, there is a lack of response from their side.

(3) Chance of misinterpretation ●     Informants may not understand the correct sense of some questions, and may not answer them. Sometimes, informants may provide vague and ambiguous answers.
(4) Time-consuming ●     The process is time-consuming, particularly when the information is to be obtained by post.


Q.2 What is a questionnaire? State the prerequisites of a good questionnaire.


What are the qualities of a good questionnaire?

(A) Meaning of questionnaire A questionnaire is a list or set of printed questions, which is filled by the informants. If it is filled by the enumerators, then it is known as a schedule.
(B) A good questionnaire should have the following characteristics:
(1) Simple and short questions Questions should be short, simple, and straightforward.
(2) Limited questions in a proper order The number of questions should be limited and they should be in a logical order.
(3) Clear instructions To assist the informants, clear instructions should be given.
(4) Pre-testing To know the shortcomings of a questionnaire, it should be tried on a small selected group.
(5) Avoid mathematical calculations Questions containing mathematical calculations should be completely avoided.
(6) Avoid personal or controversial questions Personal questions affecting sentiments and controversial questions related to religion, politics, etc., should be avoided.
(7) Secrecy assurance Respondents should be given assurance that their response will not be shared with anyone.
(8) Cover letter To convey the purpose of how it will help the parties involved, a precise cover letter should be enclosed.

Questionnaire Filled By Enumerators Method

Q.1 Explain the questionnaires filled by enumerators method of collecting primary data along with its merits and demerits.
(A) Questionnaires filled by enumerators Under this method, an enumerator personally visits informants along with a questionnaire, asks questions, and notes down their response in the questionnaire in his own language.
(B) Following are the merits of questionnaires filled by enumerators:
(1) Accurate and reliable Since the investigator has direct contact with the respondents, it is possible to get accurate and reliable information.
(2) Better responses The presence of the enumerator may induce the respondents to give information.

So, the chances of no response like in the case of mailed questionnaire method are less.

(3) Useful in case of illiterate respondents Unlike the mailed questionnaire method, this method can be used even if the respondents are illiterate.
(C) Following are the demerits of questionnaires filled by enumerators:
(1) Costly method This method is very expensive as expenditure on training, remuneration, and conveyance is to be borne by the investigator.
(2) Time consuming This method is very time consuming as the enumerator has to visit the informants personally.
(3) Inefficiency and personal bias Inefficiency or inability on the part of the enumerators due to the lack of proper training, coupled with personal bias, may adversely affect the results of the enquiry.

Students can explore this important concept by clicking on this link provided below:

Meaning of Statistical Enquiry, Meaning of Collection of Data and Sources of Data

Collection Of Secondary Data

Q.1 What is secondary data? Discuss the various sources of secondary data.
(A) Meaning of secondary data ●     Secondary data refers to the data that has already been collected by some other person or agency and is used by us.
(B) Sources of secondary data can broadly be classified under two


1. Published sources

2. Unpublished sources

(1) Published sources Published sources mean data available in printed form. It includes the following:

  1. Magazines, journals, and periodicals published by various government, semi-government, and private organisations; Data related to birth, death, education, etc., by the government at various levels; data regarding prices, production, etc., published by Economic Times, Financial Express, etc.
  2. Reports of various committees or commissions like reports of pay commission report, finance commission report, etc.
  3. Reports of international agencies that are regularly published by agencies like UNO, WHO, IMF., etc.
(2) Unpublished sources ●     All the statistical material is not always published.

●     This category includes the records maintained by various government and private offices.

●     It includes the research done by scholar students or some institutions.

●     Sources like reports prepared by private investigation companies can also be used depending upon the need.


Q.2 What precautions shall we take while using secondary data?
Following are the main precautions to be taken while using secondary data:
(1) Reliable agency ●     We must ensure that the agency that has published the data should be reliable.
(2) Suitability for the purpose of enquiry ●     The investigator must ensure that the data is suitable for the purpose of the present enquiry.

●     The suitability of the data is determined by investigating the nature, objectives, time of collection etc., of the secondary data.

(3) Adequacy and accuracy to avoid impact of bias ●     It is necessary to use adequate data to avoid biases and prejudices leading to incorrect conclusions.
(4) Method of collecting data used ●     The investigator should also ascertain as to what method was used in collecting the data.

●     Sampling methods may be biased depending upon the mode of selection of samples.

●     All these should be ascertained before making use of the secondary data.

The above-mentioned concept is for CBSE Class 11 Statistics for What are the Sources of Data. For solutions and study materials for Class 11 Statistics, visit BYJU’S or download the app for more information and the best learning experience.

Frequently Asked Questions on Sources of Data


What are the types of sources of data?

There are two types of sources of data which are:

  1. Internal sources
  2. External sources

What are the 3 sources of data?

The three sources of data are primary, secondary and tertiary.


What are the methods of primary data collection?

The following are basic or traditional methods of primary data collection:

  1. Direct personal interviews
  2. Indirect personal interviews
  3. Questionnaires
  4. Focus groups
  5. Observation


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