Class XI:Statistics [Ch-2 Collection of Data]

Collection

Collection of data is the first step in the process of statistical study. 

Data can be collected from two sources

1. Primary Source of Data

2. Secondary Source of Data

1. Primary Source of Data

It implies collection of data from its source of origin. It offers you first hand quantitative information relating to your statistical study. 

2. Secondary Source of Data

It implies collection of data from some agency or institution which already happens to collect the data. It does not offer you first hand data.

Difference Between Primary and Secondary Data

Basis	Primary Source of Data	Secondary Source of Data
Originality	It is original.	It is not original.
Objective	It is related to the specific objective of the investigator.	It is not as per the specific objective of the investigator.
Cost	Costlier than secondary sources in terms of money and time.	It is cheaper than the primary source in terms of time and money.

Methods of Collecting Primary Data

These are some popular methods of collecting primary data

Personal Investigations 

1. Direct personal investigation

2. Indirect oral investigation

3. Information from local sources or correspondents

Information Through Questionnaires and Schedules

1. Making questionnaires surveys

2. Enumerators method 

Method	Meaning	Merits	Demerits
Direct Personal Investigation	Data are personally collected by the investigator from the respondent.	High degree of original data. Accurate and reliable.	Difficult to cover a wide area. It is a very costly method.
Indirect Oral Investigation	Information will be collected from a person to our expected to have the necessary information about the person regarding whom the information is regarded.	Wide coverage, less expensive and sometimes correct information.	Doubtful and less accurate.
Information from Local Sources or Correspondence	Investigator appoints local persons or corresponce at different places.	Economy and wide coverage.	Less accurate, delay in collection and loss of originality.
Questionnaire Method	It is a tool of research when an answerer sends his answer through mail to the researchers.	Simple is not limited to access to technology such as phone or internet.	Can have a low response rate if the person viewing the questionnaire is junk mail.
Enumerator Method	Under this method the enumerator himself fills the schedules after seeing information from the informants.	It is economical, because we do not have to collect all the data. Instead of getting data from 5000 farmers, we get it from 50-100 only.	Methods, such as purposive sampling may not provide a simple, that is representative.

Qualities of a Good Questionnaire

1. Number of questions should be limited and related to the purpose only.

2. The language of the questions should be similar.

3. Questions must be placed in a proper order.

4. No undesirable questions.

5. Questions should not include complex calculations.

6. Instruction should be clear.

7. It should be pretested or cross verified.

8. Requests for the return should be mentioned.

Explain the Various Types of Questionnaire

1. Structured Questionnaire

It is a document that consists of a set of standardized questions with a fixed scheme, which specifies the exact wording and order of the questions, for gathering information from respondents.

2. Under-structure Questionnaires

The questionnaire in this case has a basic structure and some branching questions but nothing that limits the responses of a respondent.

Telephonic Interview

The investigator seeks the desired information from the respondent over the telephone.

Merits

Original accurate and reliable data collected at less expenses.

Demerits

Response ratio is very less.