Introduction to statistics

INTRODUCTION TO
STATISTICS
Dr.AnkitaChaturvedi
Dr. Ankita Chaturvedi

DATA AND STATISTICS
 Data consists of information coming from observations, counts, measurements, or
responses
 Statistics is the science of collecting, organizing, analyzing, and interpreting data
in order to make decisions.
- Statistics is a set of decision making techniques which aids businessmen
in drawing inferences from the available data

ORIGIN OF STATISTICS
 The term statistics has its origin in Latin word Status, Italian word Statista or
German term Statistik. All the three terms mean Political State.
 In ancient periods ,the beginning of statistics was made to meet the administrative
needs of the state.
 In modern times, statistics is not related to the administration of the state alone,
but it has close relation with almost all those activities of our lives which can be
expressed in quantitative terms.

MEANING OF STATISTICS
The term statistics has been generally used in two senses-
(1)Plural sense and (2)Singular sense.
 In plural sense, the term statistics refers to numerical data or statistical data. Statistics, when
used as a plural noun, may be defined as data qualitative as well as quantitative, that are
collected, usually with a view of having statistical analysis.
 In singular sense, the term statistics refers to a science in which we deal with the techniques or
methods for collecting, classifying, presenting, analyzing and interpreting the data. It means it is
‘science of counting’ or ‘science of averages’. These devices help to simplify the complex data
and make it possible for a common man to understand it without much difficulty.

DEFINITION
 “Statistics are numerical statement of facts in any department of enquiry placed in
relation to each other.”
 -A.L.Bowley
 “Statistics may be defined as the science of collection, presentation analysis and
interpretation of numerical data from the logical analysis.”
 -Croxton and Cowden
 “Statistics is the science of learning from data, and of measuring, controlling and
communicating uncertainty
 -American Statistical Association (ASA)

Some more definitions

The definition of Statistics as given by Horace Secrist
 “Statistics is the aggregate of facts affected to mark extent
by the multiplicity of causes, numerically expressed, enumerated or
estimated according to a reasonable standard of accuracy, collected in a
systematic manner for the predetermined purpose and placed in relation to
each other”.

CHARACTERISTICS OF STATISTICS
 Statistics are Aggregate of Facts
 Statistics are Affected to a marked Extent by Multiplicity, of Causes
 Statistics are Numerically Expressed
 Statistics are Enumerated or estimated according to Reasonable
Standards of Accuracy
 Statistics are Collected in a Systematic Manner
 Statistics for a Pre-determined Purpose
 Comparable

Types/ Classification of Data
Primary data is the data
collected for the first time
through personal experiences
or evidence, particularly for
research. It is also described
as raw data or first-hand
information
Secondary data are second-
hand data that is already
collected and recorded by
some researcher for their
purpose and not for the
current research problem.

Difference
Basis Primary Data Secondary Data
Definition Primary data are those which are collected
for the first time.
Secondary data refers to those data
which have already been collected by
some other person.
Originality Primary data is original because these are
collected by the Investigator for the first
time.
Secondary data are not original because
someone else has collected these for his
own purpose.
Nature of data Primary data are in the form of raw
materials.
Secondary data are in the finished form.
Reliability and
Suitability
Primary data are more reliable and suitable
for the enquiry because it is collected for a
particular purpose.
It is less reliable and less suitable as
someone else has collected the data
which may not perfectly match our
purpose.

Basis Primary Data Secondary Data
Time and Money Collecting primary data is quite expensive
both in time and money terms.
Secondary data requires less time and
money so it is economical.
Precaution and
Editing
No special precaution or editing is required
while using primary data as these have
been collected with a definite purpose.
Both precaution and editing are essential
as secondary data were collected by
someone else for his own purpose.
Data Collection
Source
Primary data can be collected through
Surveys, observations, experiments,
questionnaires, focus groups, interviews,
etc.,
secondary data are collected through
books, journals, articles, web pages,
blogs, etc.

Methods of Collecting Primary Data
1. Direct Personal Investigation
2. Indirect Oral Investigation
3. Information Through Correspondents
4. Telephonic Interview
5. Mailed Questionnaire
6. Schedules filled by enumerators

Some important terms
Investigator •One who conducts the investigation i.e. statistical
enquiry and seeks information is known as Investigator.
•It can be an individual person or an organization.
Enumerators •Enumerators are the persons who help the
Investigators in the collection of data.
Informant •Informants are the respondents who supply the
information to the investigator or enumerators.

Methods of Collecting Primary
Data
Direct Personal Investigation •Under this method, the Investigator obtains the first-hand information
from the respondents themselves.
•He personally visits the respondents to collect information (data).
Indirect Oral Investigation Under this method, instead of directly approaching the informants, the
investigators interviewed several other persons who are directly or
indirectly in touch with the informants.
Information through
Correspondents
Under this method, local agents or correspondents are appointed and
trained to collect the information from the respondents.
Telephonic Interviews Under this method, data are collected through an interview over the
telephone.

Mailed Questionnaire
Method
Under this method, a questionnaire containing a number of questions
related to the investigation is prepared.
It is then sent to Informants by post along with the instructions to fill.
The Informant after filling up the questionnaire sends it back to the
Investigator.
Schedules Filled By
Enumerators Method
Under this method, Enumerator personally visits Informants along with
a schedule, asks questions and note down their response in the
schedule in his own language.

Difference between
Questionnaire and Schedule
Basis Questionnaire Schedule
Meaning Questionnaire refers to a technique of data
collection which consist of a series of
written questions along with alternative
answers.
Schedule is a formalized set of
questions, statements and spaces for
answers, provided to the
enumerators who ask questions to
the respondents and note down the
answers
Filled by Respondents Enumerators
Response Rate Low High
Coverage Large Comparatively small
Cost Economical Expensive

Basis Questionnaire Schedule
Respondent's
identity
Not known Known
Success relies
on
Quality of the questionnaire Honesty and competence of the
enumerator.
Usage Only when the people are literate and
cooperative.
Used on both literate and illiterate
people.
Use of
Abbreviations
Can not be used Can be used
Observation
Method
Not applicable Applicable
Important
features
required
· Simple to understand
· Short questions
· Interesting and Engaging
No special features required

Collection Of Secondary Data
Sources of secondary data can broadly be classified under two Categories:
 1. Published sources
Published sources mean data available in printed form. It includes:
1. Magazines, Journals & Periodicals published by various Government, Semi-
government and Private organisations. Like, data related to birth, death, education etc.
by the government at various levels; data regarding Prices, Production etc. published
by Economic Times, Financial Express etc.
2. Reports of various Committees or Commissions. Like, report of Pay Commission
Report, Finance Commission Report etc.
3. Reports of International Agencies- Reports are regularly published by agencies like
UNO, WHO, I.M.F. etc.

Collection Of Secondary Data
 2. Unpublished sources
• All statistical material is not always published.
• This category included:
• i. Records maintained by various government and private offices.
• ii. Research studies were done by scholar students or some institutions.
• iii. Reports prepared by Private Investigation companies etc.
• Such sources can also be used depending upon the need.

Limitations of Statistics
 Statistics laws are true on average. Statistics are aggregates of facts. So single
observation is not a statistics, it deals with groups and aggregates only.
 Statistical methods are best applicable on quantitative data.
 Statistical methods cannot be applied to heterogeneous data.
 If sufficient care is not exercised in collecting, analyzing and interpretation the data,
statistical results might be misleading.
 Only a person who has an expert knowledge of statistics can handle statistical data
efficiently.
 Statistics relies on estimates and approximations. Thus the statistical inferences
are uncertain or can be misleading.

Scrutiny of Data
 Once the data are collected and always they have to be verified for their
homogeneity and consistency. This verification of data is called as scrutiny of data
 No hard and fast rules can be recommended for the scrutiny of data. One must
apply his intelligence, patience and experience while scrutinizing the given
information.

Scrutiny of Data
Scrutiny of primary data
 Errors in data may creep in while writing or copying the answer on the part of the enumerator. A
keen observer can easily detect that type of error.
 The bias of the enumerator also may be reflected by the returns submitted by him.
Scrutiny of secondary data
 Scrutinizing the secondary data is vital, because the data may be inaccurate, unsuitable or
inadequate.
 Data collected by other people cannot be fully depend upon as they may contain many pitfalls and
unless they have been thoroughly verified they should not be used.

Introduction to statistics

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