# CBSE Revision Notes for Class 11 Statistics Economics Chapter 2 – COLLECTION OF DATA – Free PDF Download

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 Chapter Name COLLECTION OF DATA Chapter Chapter 2 Class Class 11 Subject Statistics Economics Revision Notes Board CBSE TEXTBOOK Statistics Economics Category REVISION NOTES

## CBSE Class 11 Statistics Economics Revision Notes for COLLECTION OF DATA of Chapter 2

Data is a collection of facts and measurement.
Data is a tool which helps in reaching a sound conclusion by providing information therefore. For statistical investigation, collection of data is the first and foremost.
Sources of Data
1. Primary Source
2. Secondary Sources
a. Published sources
b. Un-published sources
Primary Data– Data originally collected in the process of investigation are known as primary data. This is original form of data which are collected for the first time.It is collected directly from its source of origin.
Methods of collecting primary data
There are three basic ways of collecting data :
(i) Personal interview OR Direct Personal Investigation
(ii) Mailing (questionnaire surveys)
(iii) Telephone interviews
(iv) Indirect verbal investigation
(v) Information from local sources
(vi) Enumerator method
Secondary data It refers to collection of data by some agency, which already collected the data and processed. The data thus collected is called secondary data.
Point of difference between Primary and Secondary data :-
1. Accuracy,
2. Originality,
3. Cost,
4. Need of modification

 BASIS FOR COMPARISON PRIMARY DATA SECONDARY DATA Meaning Primary data refer to the first hand data gathered by the researcher himself. Secondary data means data collected by someone else earlier. Data Real time data Past data Process Very involved Quick and easy Source Surveys, observations, experiments, questionnaire, personal interview, etc. Government publications, websites, books, journal articles, internal records etc. Cost effectiveness Expensive Economical Collection time Long Short Specific Always specific to the researcher’s needs. May or may not be specific to the researcher’s need. Accuracy and Reliability More Relatively less

Sources of secondary data
Published sources
1. Govt. publication
2. semi-Govt. Publication
3. Reports of committees & commissions
4. Private publications e.g., Journals and News papers research institute, publication of trade association.
5. International publications
Unpublished Sources
The statistical data needn’t always be published. There are various sources of unpublished statistical material such as the records maintained by private firms, business enterprises, scholars, research workers, etc. They may not like to release their data to any outside agency.
Other source : web-site
Important points to be kept in mind while drafting the questionnaire
A. Introduction and purpose of investigation
B. Reasonable number questions.
C. Questions should be small & clear.
D. Questions should be arranged logically.
E. Instructions should be clear.
G. Questions should be relevant to the investigation.
H. Personal questions should be avoided.
I. Avoid questions of calculations.
J. Cross Verification.
H. The question should not be ambiguous.
I. The question should not use double negative like “don’t you”.
J. The question should not indicate alternative answers.
Pilot Survey: Before sending the questionnaire to the information. It should be pretested. As a result of its short comings if any, can be removed. Such pretesting named as pilot survey.
A pilot survey is a preliminary survey used to gather information prior to conducting a survey on a larger scale. Pilot surveys, typically taken by smaller groups, help determine the efficiency of the future survey while also helping organizations smooth out difficulties before administering the main survey.
Methods of sampling:
1. Random sampling
a. Simple or unrestricted random sampling
b. Restricted random sampling
i. Stratified
ii. systematic
iii. multistage or cluster sampling
2. Non-Random Sampling
a. Judgment sampling
b. Quota sampling
c. Convenience sampling
Census survey : In this method every element of population is included in the investigation.
Sample survey : In this method a group of units representing all the units of the population is investigated.

 BASIS FOR COMPARISON CENSUS SAMPLING Meaning A systematic method that collects and records the data about the members of the population is called Census. Sampling refers to a portion of the population selected to represent the entire group, in all its characteristics. Enumeration Complete Partial Study of Each and every unit of the population Only a handful of units of the population. Time required It is a time consuming process. It is a fast process. Cost Expensive method Economical method Results Reliable and accurate Less reliable and accurate, due to the margin of error in the data collected. Error Not present. Depends on the size of the population Appropriate for Population of heterogeneous nature. Population of homogeneous nature.

Population or universe
In Statistics, population or universe simply refers to an aggregate of items to be studied for an investigation.
Sample: A group of items taken from the population for investigation and representative of all the items.
Sampling Errors: Sampling error is the difference between the result of studying a sample and the result of the census of the whole population.
Non-Sampling Error: Can occur in any type of survey whether it be a census or sample survey.
Sampling errors
1. Biased errors
2. Unbiased errors
Non sampling errors
1. Error in data acquisition
2. Non Response error
3. Sampling Bias
Census of India and National Sample Survey Organization:
The census of India provides the complete and continuous demographic record of population.
The NSSO was established by the Govt. of India to conduct nation wide survey on socio-economic issues like employment, literacy, maternity, child care, utilisation of public distribution system etc.
The data-collected by NSSO survey are released through reports and its quarterly journal ‘’Sarvekshana’’.
Eg. Size, growth rate, distribution of population, density, population, projections, sex composition and literacy.
These data are used by govt. of India for planning purpose.