Notes - Collection of Data Class 11, Statistics for Economics | EduRev Notes

COLLECTION OF DATA

Points to remember:

1. Collection of data is the first important aspect of statistical survey.

2. Data – Information which can be expressed in numbers.

3. Two sources of data – Primary & Secondary Primary data – data collected by investigator himself secondary data – data collected by someone and used by the investigator.

4. Difference between Primary and Secondary Data

a] Primary data is original data collected by the investigator while secondary data is already existing and not original.

b] Primary data is always collected for a specific purpose while secondary data has already been collected for some other purpose.

c] Primary is costlier or is more expensive whereas secondary data is less expensive.

5. Methods / Sources of Collection of Primary Data :

a] Direct Personal Interview – Data is personally collected by the interviewer.

b] Indirect Oral Investigation – Data is collected from third parties who have information about subject of enquiry.

c] Information from correspondents – Data is collected from agents appointed in the area of investigation.

d] Mailed questionnaire – Data is collected through questionnaire [list of questions] mailed to the informant.

e] Questionnaire filled by enumerators – Data is collected by trained enumerators who fill questionnaires.

f] Telephonic interviews – Data is collected through an interview over the telephone with the interviewer.

Questionnaire – A list of questions with space for answers.

6. Pilot Survey – Try-out of the questionnaire on a small group to find its short comings.

7. Qualities of a good questionnaire :

a] A covering letter with objectives and scope of survey.

b] Minimum number of questions.

c] Avoid personal questions.

d] Questions should be clear and simple.

e] Questions should be logically arranged.

8. Difference between census method and sampling method.

1.Census Method – Data collected from each and every unit of population.

2.Sample Method – Data is collected from few units of the population and result is applied

to the whole group.

3.Universe or population in statistics – Total items under study.

4.Sample is a section of population from which information is to be obtained.

Sources of Secondary Data:

1. Published Source – Government publications, Semi-government publications etc.

2. Unpublished Source – Census of India [They are collected by the organizations for their own record]

Sampling Methods: 1] Random sampling 2] Non-random sampling

1. Random Sampling – It is a sampling method in which all the items have equal chance of being selected and the individuals who are selected are just like the ones who are not selected.

2. Non-random sampling – It is a sampling method in which all the items do not have an equal chance of being selected and judgment of the investigator plays an important role.

Types of Statistical errors:

1] Sampling errors 2] Non-sampling errors

Sampling Error: It is the difference between sample value and actual value of a characteristic of a population.

Non-sampling errors: Errors that accurate the stage of collecting data.

Types of non-sampling errors:

a] Errors of measurement due to incorrect response.

b] Errors of non-response of some units of the sample selected.

c] Sampling bias occurs when sample does not include some members of the target population.

Census of India – It provides complete and continuous demographic record of population.

National Sample Survey Organization – It conducts national surveys on socio-economic issues.

Sarvekshana – Quarterly journal published by NSSO.