Statistical enquiry means search conducted by statistical methods. One who conducts this type of enquiry is called INVESTIGATOR and those from whom statistical information is collected are known as respondents or INFORMANTS.


(1)        Internal :

Internal data is the one which is available with the organization about sales, production, salary, wages.

(2)        External :

Information collected outside the agencies is called external data which can be PRIMARY OR SECONDARY DATA.

(a)        Primary Data :

Primary  data is the external and first hand information. It is collected originally. It is collected and used by the same person. It is time consuming.

(b)        Secondary Data :

It is the second hand information collected through different sources. It is collected and used by different persons. It is time saving.

For example :

Any government publication is a primary data for the government but secondary data for research worker.



  • Direct Personal Interview:According to this method, data is collected by investigator personally from the persons who are the subject of enquiry. This method of data collection is used when area of enquiry is limited or when maximum degree of accuracy is required.

Merits :

(a)        Original Data is collected by this method.

(b)        Informants reactions to the questions can be properly studied.

(c)        There is a flexibility in the enquiry as investigator is personally present.

Demerits :

(a)        This method cannot be used when field of enquiry is wide.

(b)        It is costly and consumes time.

(c)        Personal biasness can give wrong results.

(d)        It is complicated and lengthy.


  • Telephonic Interview :The investigator asks questions over landline, telephone, mobile telephones and even through websites. These days online services through “short message service” i.e. SMS has been popular.

Merits :

(a)        Telephonic interviews are simpler than personal interview.

(b)        It can be conducted in a shorter period of time.

(c)        Sometimes the respondents are reluctant to answer the questions in the personal interview.

Demerits :

(a)        Information cannot be obtained from those who do not have phones.

(b)        Reactions of the respondents cannot be judged.

(iii)       Information From Correspondence :In this method, local agents and correspondents are appointed in different part of investigation area. These agents regularly supply information to the central office or investigator. Radio and newspaper agencies generally obtain information by this method. It is suitable when

(a)        The information is to be obtained from wide area.

(b)        When degree of accuracy is not required.

Merits :

(a)        It can cover wide area under investigation.

(b)        It gives result easily and promptly.

Demerits :

(a)        Original data is not obtained.

(b)        It gives approximate and vague results.

(c)        There can be a personal biasness which may affect the accuracy of the information sent.

(iv)       Mailed Questionaire :A list of questions relating to the enquiry is called schedule or questionnaire. A list of questions provide a space for each answer.Schedule are sent to the information by post with a request to answer and return it within a specified time period. The success of this method depends on the co-operation that the informant is prepared to give and the manner in which the questionnaire is drafted.

Merits :

(a)        Large field can be studied by this method.

(b)        This is not expansive method.

(c)        We can obtain original data by this method.

(d)        It is free from any kind of personal biasness as the information is given by informants themselves.

Demerits :

(a)        It is difficult to presume the co-operation on the part of informants.

(b)        Schedule sent back may be incomplete or inaccurate.

(c)        There may be delay in getting the re ply from the informants.

(d)        This method can be used only when the informant is educated and literate.

(e)        There may be loss of questionnaire in transit.


  1. When it is compulsory by law to fill the questionnaire e.g. Government agencies compel banks and companies etc. to supply information to the government in the prescribed form.
  2. This method can be successful when informant is educated.


Following precautions must be taken while drafting a questionnaire.

  1. Covering Letter : – A personal letter can be enclosed indicating the purpose and the aims of enquiry. A self-addressed and stamped envelope,should be enclosed for the convenience of the respondents to return the questionnaire.
  2. More is the number of questions, less is the possibility of response. Lengthy questions should be divided into parts and irrelevant questions should be eliminated.
  3. Personal questions which may disclose the confidential, private or personal information should be avoided.
  4. The questions should be simple and easy to understand by the informants.
  5. Instructions should be provided to the informant about when and where to return the questionnaire.
  6. Questions must be framed in an objective manner so that informants can give answer quickly and promptly.
  7. The questions must start from the general and move to the specific one.
  8. Questionaire should be made as attractive as possible.
  9. The questions which involve mathematical calculation should be avoided.
  10. Some questions should provide the means of checking inaccuracies in the answers e.g. question of age and date of birth is a cross check.
  11. Before taking the enquiry on a large scale, the questionnaire drafted should be pre-tested with a small number of group of people.


Secondary data are those which are collected by some other agency and are used for further studies. It may be either (a) Published (b) Unpublished.

Published Source

  1. Government Publications :Different ministries and department of centre and state government publish regularly current information along with statistical data on the number of subjects like annual survey of industries, agriculture statistics of India.
  2. Publication of International Organisation :International statistics can be obtained from the publications of different international organization like UNO (United Nation Organisation), IMF (International Monetory Fund) and World Bank etc.
  3. Sub Official Publications :Local bodies such as municipal Corporations, district board etc. publish a periodical report which provide information about health, sanitation, birth, death etc.
  4. Reports of Committee and Commission :Various committee and commissions are appointed by the central and state government for some special study and recommendations some of the reports are – report of national agriculture commission, report of the tariff commission.
  5. Private Publications :

(a)        Journal and Newspaper :Journal and newspaper like financial express, economic times, Eastern Economics Collects and regularly publish the data on different fields of economics commerce and trade.

(b)        Research Institutions :The national council of applied economics research and foundation of scientific and economic research are such institutions.

(c)        Professional Trade Bodies :Professional trade bodies like Federation of Indian chamber of commerce, Institute of chartered accounts, sugar mill association, publish the statistical data.

(d)        Annual Reports :These are published by the companies every years.

(e)        Articles, Market Reviews and Reports :

Unpublished Source

Sometimes, the data on the valuable subject is collected but it is not published. This is called unpublished data.