This document discusses various methods for collecting primary data for statistical analysis. It describes primary data as data collected directly from respondents, and secondary data as data originally collected by others. Methods for collecting primary data include direct personal interviews, indirect oral investigations, mailed questionnaires, and telephonic interviews. It also discusses census and sampling methods, random and non-random sampling, and types of errors in statistical analysis like sampling errors and non-sampling errors. The document was created by Arjun Kumar, a class 11 commerce student, for his economics subject on the topic of data collection.

1. NAME – ARJUN KUMAR
CLASS – XI Com.
ROLL No. - 18
SUBJECT – ECONOMICS
TOPIC - COLLECTION OF DATA
SCHOOL – K.V. No.2 BHUJ

2. Data: – Information which can be expressed in numbers.
Two sources of data: – Primary & Secondary.
Primary Data.
The data which is collected for
the first time by investigators or
enumerators to serve a specific
purpose is called Primary data.
They are based on first-hand
information. In other words such
a data is of original in nature.
The sources from where these
data can be collected are known
as Sources.
Secondary Data.
The data which is originally
collected and published by the
authorities other than who require
it or the data which is obtained
from published or unpublished
sources is called Secondary data.
Such data is already available in
some government publications,
research study, journals or
newspaper etc.

3. Sources of Collection of Primary Data:
 Direct Personal Interview
 Indirect Oral Investigation
 Information from correspondents
 Mailed questionnaire
 Questionnaire filled by enumerators
 Telephonic interviews

4. Direct Personal Investigation
Under this method, investigators personally visit respondents, ask
them questions pertaining to the enquiry and collect the desired
information. In other words it is a method by which data are
personally collected by the investigator from the respondents or
informants. The investigator establishes direct relation with a
person from whom the information is to be obtained.
Advantages…
1. Highest response rate
2. Allows all types of questions
3. Allows clearing doubts regarding questions
Disadvantages…
1. Most expensive
2. Informants can be influenced
3. Takes more time

5. Indirect Oral Investigation
Under this method, investigator collect data by contracting with the
third party or informants who are supposed to possess the
information on the problem under investigation. In other words the
data will be collected from those persons who may possess some
knowledge about the investigation. Such persons are known as
“Witnesses”.
Advantage… Disadvantage…
1. Less Expensive 1. Lack of Accuracy
2. Experts Opinion 2. Lack of Uniformity
3. Wide Coverage 3. Lack of Reliability

6. Telephonic interviews
In a telephone interview the investigator asks questions over the
telephone. The investigator instead of presenting himself before
the informants contacts them via telephone and collects the
desired information.
Advantages… Disadvantages…
1) Relatively low cost 1) Limited use
2) Relatively high response rate 2) Reactions cannot be
watched
3) Less influence on informants 3) Respondents can be
influenced

7. Information from correspondents
According to this method, the correspondents or local agencies in
different regions collect the required information in their own
way and subsequently submit their reports or transmit the
information to the central office where data are processed and
finally analyzed. When the information is to be collected
regularly on a timely basis (daily, weekly or monthly)
correspondents may be posted at various places. This method is
usually adopted by newspaper agencies that require political
information in areas like sports, economic trends, share markets,
law and order etc.

8. Mailed questionnaire
Under this method, a well-designed questionnaire is mailed to the
informants with a request to fill it up and return the same within the
specific time schedule. It is pointed out in the covering letter to the
correspondents that information supplied by them in the
questionnaire will be kept secretly confidential. In the prevalent
knowledge based environment, an investigator may e-mail the
questionnaire to target group of respondents and can mobilize the
desired information subject to certain conditions. The success of this
method is based on the ability to design the questionnaire,
knowledge of the respondents and their response to questionnaire.

9. Questionnaire filled by enumerators
Under this method, a well-designed questionnaire is mailed to the
informants with a request to fill it up and return the same within
the specific time schedule. It is pointed out in the covering letter to
the correspondents that information supplied by them in the
questionnaire will be kept secretly confidential. In the prevalent
knowledge based environment, an investigator may e-mail the
questionnaire to target group of respondents and can mobilize the
desired information subject to certain conditions. The success of this
method is based on the ability to design the questionnaire,
knowledge of the respondents and their response to questionnaire.

10. The two popular approaches used by the
statistician...
• A survey, which includes
every element of the
population, is known as
census or method of
complete enumeration. In
other words when data are
collected for each and every
unit of the investigation, it is
called census method.
Sampling Method
• Sampling investigation refers to
the process of learning about the
population on the basis of sample
drawn from it. In sampling
method instead of every items of
the universe only a part of the
universe is studied and
conclusions are drawn on the
same basis for entire universe.
Census Method

11. Difference between Census method and
Sampling method…
Census Method
• Every unit of population studied.
• Reliable and accurate results.
• Expensive method.
• Suitable when population is of
homogenous nature.
Sampling Method
• Few units of population are studied.
• Less Reliable and accurate results.
• Less expensive method.
• Suitable when population is of
heterogeneous nature.

12. Types of
Sampling
Random
Sampling
Unrestricted
Random
Sampling
Restricted
Random
Sampling
Non-Random
Sampling

13. Random Sampling
When every item of the population or universe can have an equal
chance (equal opportunity) of being selected in sample, it is
known as random sampling. In other words under this method,
sample from universe is taken at random. It is also known as
“Probability Sampling” or “Representative Sampling”. Personal
interests or bias of investigator does not affect the selection of the
sample. There are two methods under Random Sampling:-
(a) Simple or Unrestricted Sampling.
(b) Restricted Random Sampling.

14. Non- Random Sampling
In a non- random sampling method, all the units or
items of the universe do not have an equal chance of
being selected and convenience or judgement of the
investigator or enumerator plays an important role in
the selection of items in the sample. Samples are
selected on the basis of judgement, purpose,
convenience or quota.

15. Sampling and Non-Sampling Errors
Sampling Errors
Sampling errors refers to the
difference between the sample
estimated and the actual value of
characteristics of the population
or universe. It is error that occurs
when we make an observation
from the population. The
difference between the actual
value of a parameter of the
population and its estimate is the
sampling error. The magnitude of
sampling error can be reduce by
taking a large sample from the
Non-Sampling Errors
These errors can occur in any type
of survey whether it be a census or
sample survey. Non-sampling
errors are more serious than
sampling errors. Some of the non-
sampling errors are as follows:-
• Errors in Data Acquisition
• Non-Response Errors
• Sampling Bias
• Measurement Errors

16. The End…
Thank you…
Sub.-Statistics {Eco.}
Made By- Arjun Kumar