chapter8 sampling
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Business
Research Methods
Sample Designs and Sampling
Procedures
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Fundamental Idea of Sampling
The fundamental idea of sampling is that by
selecting a few elements from a population,
we can make conclusion about the whole
population.
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Inferential Process
Population
Sample
Sample
Statistics
Estimation
& Test
),( spX
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Parameter and Statistic
Example
The average height of MBA students is
150 cms.
Parameter
The average height of students in the
AGW 621 class is 150 cms.
Statistic
Population
Sample
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SAMPLING TERMINOLOGY
Population
All items of interest
Element
Members of a population
Sample Portion chosen from population
Subject
Members of a sample
Parameter
Characteristic of a population Statistic
Characteristic of a sample
Census
Population is very small
There is a lot of variation among elements
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Why Sample
Cost
Time
Destruction of unit More accurate
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Define the target population
Select a sampling frame
Conduct fieldwork
Determine if a probability or
nonprobability sampling method
will be chosen
Plan procedure for selecting
sampling units
Determine sample size
Select actual sampling units
Stages in the Selection
of a Sample
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TARGET POPULATION
RELEVANT POPULATION
OPERATIONALLY DEFINE
COMIC BOOK READER?
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SAMPLING FRAME
A LIST OF ELEMENTS FROM WHICH
THE SAMPLE MAY BE DRAWN
WORKING POPULATION
MAILING LISTS - DATA BASE
MARKETERS
SAMPLING FRAME ERROR
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SAMPLING UNITS
GROUP SELECTED FOR THE SAMPLE
PRIMARY SAMPLING UNITS (PSU)
SECONDARY SAMPLING UNITS
TERTIARY SAMPLING UNITS
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RANDOM SAMPLING ERROR
THE DIFFERENCE BETWEEN THE
SAMPLE RESULT SAND THE RESULT
OF A CENSUS CONDUCTED USINGIDENTICAL PROCEDURES
STATISTICAL FLUCTUATION DUE TO
CHANCE VARIATIONS
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SYSTEMATIC ERRORS
NONSAMPLING ERRORS
UNREPRESENTATIVE SAMPLE
RESULTS
NOT DUE TO CHANCE
DUE TO STUDY DESIGN OR
IMPERFECTIONS IN EXECUTION
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ERRORS ASSOCIATED WITH
SAMPLING
SAMPLING FRAME ERROR
RANDOM SAMPLING ERROR
NONRESPONSE ERROR
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TWO MAJOR CATEGORIES OF
SAMPLING
PROBABILITY SAMPLING KNOWN, NONZERO PROBABLITY FOR
EVERY ELEMENT
NONPROBABLITY SAMPLING PROBABLITY OF SELECTING ANY
PARTICULAR MEMBER IS UNKNOWN
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Sampling Design
Judgment
Quota
Convenience
Judgment
Single Stage
Multi-Stage
Simple Random
Systematic
Cluster
Stratified
Simple Random
Stratified
Combination
Non-probability
design
Probability design
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NONPROBABLITY SAMPLING
CONVENIENCE
JUDGMENT
QUOTA
SNOWBALL
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PROBABLITY SAMPLING
SIMPLE RANDOM SAMPLE
SYSTEMATIC SAMPLE
STRATIFIED SAMPLE
CLUSTER SAMPLE
MULTISTAGE AREA SAMPLE
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CONVENIENCE SAMPLING
also called haphazard or accidental
sampling
the sampling procedure of obtaining the
people or units that are most conveniently
available
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JUDGMENT SAMPLING
also called purposive sampling
an experienced individual selects the sample
based on his or her judgment about some
appropriate characteristics required of the
sample member
e.g., Test market
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QUOTA SAMPLING
ensures that the various subgroups in a
population are represented on pertinent
sample characteristics
to the exact extent that the investigators
desire
it should not be confused with stratified
sampling
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SNOWBALL SAMPLING
a variety of procedures
initial respondents are selected by
probability methods
additional respondents are obtained from
information provided by the initial
respondents
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SIMPLE RANDOM SAMPLING
a sampling procedure that ensures that each
element in the population will have an equal
chance of being included in the sample
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SYSTEMATIC SAMPLING
A simple process
every nth name from the list will be drawn
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STRATIFIED SAMPLING
Probability sample
Subsamples are drawn within different
strata
Each stratum is more or less equal on some
characteristic
Do not confuse with quota sample
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STRATIFIED SAMPLING
All Students
Commuters Residents
Sample
1. Divide population into
homogeneous subgroups
Mutually exclusive Exhaustive
2. Select proportionate
simple random
samples from subgroups
3. More accurately reflect
characteristics of the
population
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CLUSTER SAMPLING
The purpose of cluster sampling is to
sample economically while retaining the
characteristics of a probability sample. The primary sampling unit is no longer the
individual element in the population.
The primary sampling unit is a larger clusterof elements located in proximity to one
another.
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WHAT IS THE APPROPRIATE
SAMPLE DESIGN
Homogeneity of sampling units - variations
Confidence level required
Precision required - sampling error
Analytical procedure
Cost, time, personnel
Advanced knowledge of the population
National versus local
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AFTER THE SAMPLE DESIGN
IS SELECTED
DETERMINE SAMPLE SIZE
SELECT ACTUAL SAMPLE UNITS
CONDUCT FIELDWORK
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