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Collection of Data:
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Primary Data
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Secondary Data
Sampling:
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Concept of Sampling
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Non-Random Versus Random Sampling
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Simple Random Sampling
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Other Types of Random Sampling
As far as the objectives
of your research are concerned, they should be stated in such a way that you
are absolutely clear about the goal of your study ---
EXACTLY WHAT
IT IS THAT YOU ARE TRYING TO FIND OUT?
As far as methodology
for DATA-COLLECTION is concerned, we need to consider:
- Source of your data
(the statistical population) - Sampling Methodology
- Instrument for collecting data
COLLECTION OF DATA
The most
important part of statistical work is perhaps the collection of data.
Primary and Secondary Data
Primary Data
Data that have been originally
collected (raw data) and have not undergone any sort of statistical treatment,
are called PRIMARY data.
Secondary Data
Data that have undergone any
sort of treatment by statistical methods at least ONCE, i.e. the
data that have been collected, classified, tabulated or presented
in some form for a certain purpose, are called SECONDARY data.
COLLECTION OF PRIMARY DATA
One or more of the following
methods are employed to collect primary data:
i) Direct
Personal Investigation.
ii) Indirect
Investigation.
iii) Collection through Questionnaires.
iv) Collection
through Enumerators.
v) Collection
through Local Sources.
DIRECT PERSONAL INVESTIGATION
In this method, an investigator
collects the information personally from the individuals concerned.
Since the information collected is generally considered quite accurate and
complete.
INDIRECT INVESTIGATION
Sometimes the direct sources do not
exist or the informants hesitate to respond for some reason or other. In
such a case, third parties or witnesses having information are
interviewed.
COLLECTION
THROUGH QUESTIONNAIRES
A questionnaire is an inquiry
form comprising of a number of relevant questions with space for entering
information asked.
The questionnaires are usually sent
by mail, and the informants are requested to return the questionnaires
to the investigator after doing the needful within a certain period.
This method is cheap, fairly
expeditious and good for extensive inquiries.
COLLECTION THROUGH ENUMERATORS
Under this method, the information
is gathered by employing trained enumerators who assist the
informants in making the entries in the schedules or questionnaires correctly.
COLLECTION THROUGH LOCAL SOURCES
In this method, there is no formal collection of data
but the agents or local correspondents are directed to collect and send
the required information, using their own judgment as to the best way of
obtaining it.
COLLECTION OF SECONDARY DATA
The secondary data may be obtained
from the following sources:
i) Official,
e.g. the publications of the Statistical Division, Ministry of Finance, the
Federal and Provincial Bureaus of Statistics, Ministries of Food, Agriculture,
Industry, Labour, etc.
ii) Semi-Official,
e.g., Banks, Railway Board, Central Cotton Committee, Boards of Economic
Inquiry, District Councils, Municipalities, etc.
iii)
Publications of
Trade Associations, Chambers of Commerce, etc.
iv)
Technical and Trade Journals and Newspapers.
v)
Research Organizations
such as universities, and other institutions.
