Collection Of Data In Statistics Class 11 Notes Download In PDF
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 SecondaryData
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) Every unit of population studied
2) Reliable and accurate results
3) Expensive method
4) Suitable when population is of homogenous nature
|Few units of population are studied
Less Reliable and accurate results
Less expensive method
Suitable when population is of heterogeneous nature
9. Personal Interview Method :
| 1) Highest response rate
2) Allows all types of questions
3) Allows clearing doubts regarding questions
Informants can be influenced
Takes more time
10.Mailed Questionnaire Method:
|1) Least expensive
2) Only method to reach remote areas
3) Informants can be influenced
|Long response time
Cannot be used by illiterates.
Doubts cannot be cleared regarding questions
11.Telephonic Interview Method:
|1) Relatively low cost
2) Relatively high response rate
3) Less influence on informants
Reactions cannot be watched
Respondents can be influenced
• Census Method – Data collected from each and every unit of population.
• Sample Method – Data is collected from few units of the population and result is applied to the whole group.
• Universe or population in statistics – Total items under study.
• Sample is a section of population from which information is to be obtained.
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]
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.
1] Sampling errors.
2] Non-sampling errors
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.
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.
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.
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