Sampling_ vipin

SAMPLING
-VIPIN
PATIDAR
www.vipinpatidar.wordress.com

Introduction:-
 Researcher rarely study the whole
population of subjects.
 The safest choice is to study the whole
population.

terminology:-
 POPULATION-
 A complete set of persons or object that possess
some common Characterstics that is of interest to
the researcher.
 It is the entire aggregation of cases that meet a
specified set of criteria.
 KINDS OF POPULATION-
 Theoretical population-
 accessible population-

Contd…
 THEORITICAL POPULATION-
 The population you would like to generalize to
entire population in which researcher is
interested.
 ACCESSIBLE POPULATION-
 The population that will be accessible to
researcher.

terminology
 PARAMETER-
 The information or data collected from a
population called as parameter.
 STATISTIC-
 The information or data collected from a sample
called as statistic.
 RANDOMIZATION-
 It is the process of selecting a representation
sample of the target population ensuring that
every element in the target population has an
equal chance of being selected.

terminology
 SAMPLING ERROR
 It is difference or error between sample statistic
and the population parameters.
 SAMPLING BIAS-
 Occur when the researcher shows a preference in
selecting one participant over another.
 SAMPLING CRITERIA-
 The researcher needs criteria to determine
whether a person qualifies as a member of the
population.

terminology
 SAMPLE-
 Subset of population.
 It is the finite part of a statistical population
whose properties are studied to gain information
about whole.
Webster 1985
 SAMPLING-
 It is the act, process or technology of selecting a
suitable sample or a representative part of a
population for the purpose of determining
characteristics of the whole population.

ADVANTAGES OF SAMPLING
The lower is cost/economy.
Timeless, data collection is faster.
To improve the accuracy and quality of
data.
Inaccessibility of some of the
population.
To avoid large size of population.

SAMPLING process
Define population
Theoretical population
Accessible population
Sampling frame
Sample selection
Determine sample size
Implement sampling plan
Reviewing the sampling process

Types of sampling / approaches:-
PROBABILITY NON PROBABILITY
• SIMPLE RANDOM
•STRATIFIED SAMPLING
•SYSTEMATIC SAMPLING
•CLUSTER SAMPLING
• PURPOSIVE SAMPLING
•QUOTA SAMPLING
•CONVENIENT SAMPLING
•SNOW BALL SAMPLING

1) probability SAMPLING
1.1 SIMPLE RANDOM SAMPLING-
 Each element in the population has an
equal and independent chance of being
chosen or selection.

ADVANTAGES DISADVANTAGES
1) Eliminate research
bias
1) Time consuming
2) Required limited
knowledge about
population.
2) Rarely to get
complete list of
population.
3) Mean of estimate
sampling error
1.1 SIMPLE RANDOM SAMPLING-

1.2 STRATIFIED SAMPLING-
 Divide population into groups (strata)
that differ in important ways .
 Basis for grouping must be known
before sampling. E.g.- age, gender etc.
 Select random sample from within each
group.

1) Eliminate research
bias
1) Very complex
2) Ensure
representation of a
particular segment of
population.
2) Complete list of target
population needed.
3) Required extensive
knowledge.
1.2 STRATIFIED SAMPLING-

1.3 SYSTEMATIC SAMPLING-
 Selecting every Kth element of
the population.
 K=N/n K=sampling interval
N= total population
n= sample size

1) Fast, easy and
inexpensive.
1) Element in the
sampling frame must be
randomized.
2) Error may reduce
because of simplicity.
2) Complete list of target
population needed.
1.3 SYSTEMATIC SAMPLING-

1.4 CLUSTER SAMPLING-
 Population is divided into large groups
(cluster).
Population
Cluster-1 cluster-2 cluster-3
Sample-1 sample-2 sample-3

1) Can be cheaper than
other method.
1) Possibility of
sampling error at each
stage
2) Allow probability
sampling for a
population which is not
allotted in frame.
1.4 CLUSTER SAMPLING-

2) NON-probability SAMPLING
2.1 CONVENIENCE SAMPLING-
 Subjects selected because it is easy to
access them.
 No reason tied to purposes of research.
 Students in your class, people on State
Street, friends.

1) Easy 1) Sampling bias
2) Saving time and
money.
2) May not represent the
population.
3) Limited
generalisability
2.1 CONVENIENCE SAMPLING-

2.2 PURPOSIVE SAMPLING-
 Subjects selected for a good reason
tied to purposes of research.
 hand picking of subjects.

1) Allow researcher to
hand pick.
1) Sampling bias
2) Limited
generalisability .
2.2 PURPOSIVE SAMPLING-

2.3 QUOTA SAMPLING-
 Pre-plan number of subjects in specified
categories (e.g. 100 men, 100 women).
 The subjects chosen for those
categories are a convenience sample,
selected any way the interviewer
chooses

2.4 SNOW BALL SAMPLING-
 Initially contact a few potential
respondents and then ask them
whether they know of anybody with the
same characteristics.

Thank
you

Sampling_ vipin

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