chapter 16 sampling designs and sampling procedures © 2010 south-western/cengage learning. all...

Chapter 16Chapter 16Sampling Designs Sampling Designs

and Sampling and Sampling ProceduresProcedures

© 2010 South-Western/Cengage Learning. All rights reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

© 2010 South-Western/Cengage Learning. All rights reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

ZIKMUND BABINCARR GRIFFIN

BUSINESS MARKET RESEARCH

EIGHTH EDITION

© 2010 South-Western/Cengage Learning. All rights reserved. May not be scanned, copied or duplicated, or posted to a publically accessible website, in whole or in part. 16–2

LEARNING OUTCOMESLEARNING OUTCOMESLEARNING OUTCOMESLEARNING OUTCOMES

1.1. Explain reasons for taking a sample rather than a Explain reasons for taking a sample rather than a complete censuscomplete census

2.2. Describe the process of identifying a target population Describe the process of identifying a target population and selecting a sampling frameand selecting a sampling frame

3.3. Compare random sampling and systematic Compare random sampling and systematic (nonsampling) errors(nonsampling) errors

4.4. Identify the types of nonprobability sampling, including Identify the types of nonprobability sampling, including their advantages and disadvantagestheir advantages and disadvantages

After studying this chapter, you should be able to


LEARNING OUTCOMES (cont’d)LEARNING OUTCOMES (cont’d)LEARNING OUTCOMES (cont’d)LEARNING OUTCOMES (cont’d)

5.5. Summarize the advantages and disadvantages of the Summarize the advantages and disadvantages of the various types of probability samplesvarious types of probability samples

6.6. Discuss how to choose an appropriate sample design, Discuss how to choose an appropriate sample design, as well as challenges for Internet samplingas well as challenges for Internet sampling

After studying this chapter, you should


Sampling TerminologySampling Terminology

• SampleSample A subset, or some part, of a larger population.A subset, or some part, of a larger population.

• Population (universe)Population (universe) Any complete group of entities that share some Any complete group of entities that share some

common set of characteristics.common set of characteristics.

• Population ElementPopulation Element An individual member of a population.An individual member of a population.

• CensusCensus An investigation of An investigation of allall the individual elements that the individual elements that

make up a population.make up a population.


Why Sample?Why Sample?

• Pragmatic ReasonsPragmatic Reasons Budget and time constraints.Budget and time constraints. Limited access to total population.Limited access to total population.

• Accurate and Reliable ResultsAccurate and Reliable Results Samples can yield reasonably accurate information.Samples can yield reasonably accurate information. Strong similarities in population elements makes Strong similarities in population elements makes

sampling possible.sampling possible. Sampling may be more accurate than a census.Sampling may be more accurate than a census.

• Destruction of Test UnitsDestruction of Test Units Sampling reduces the costs of research in finite Sampling reduces the costs of research in finite

populations.populations.


EXHIBIT 16.EXHIBIT 16.11 A Photographic Example of How Sampling WorksA Photographic Example of How Sampling Works


EXHIBIT 16.EXHIBIT 16.22

Stages in the Stages in the SelectionSelectionof a Sampleof a Sample


Practical Sampling ConceptsPractical Sampling Concepts

• Defining the Target PopulationDefining the Target Population What is the relevant population?What is the relevant population? Whom do we want to talk to?Whom do we want to talk to?

Population is operationally defined by specific and explicit Population is operationally defined by specific and explicit tangible characteristics.tangible characteristics.

• The Sampling FrameThe Sampling Frame A list of elements from which a sample may be drawn; A list of elements from which a sample may be drawn;

also called working population.also called working population. Sampling Frame ErrorSampling Frame Error

Occurs when certain sample elements are not listed or are Occurs when certain sample elements are not listed or are not accurately represented in a sampling frame.not accurately represented in a sampling frame.


EXHIBIT 16.EXHIBIT 16.33 Mailing List Directory PageMailing List Directory Page


Practical Sampling Concepts (cont’d)Practical Sampling Concepts (cont’d)

• Sampling services (list brokers)Sampling services (list brokers) Provide lists or databases of the names, addresses, Provide lists or databases of the names, addresses,

phone numbers, and e-mail addresses of specific phone numbers, and e-mail addresses of specific populations.populations.

Reverse directoryReverse directory A directory similar to a telephone directory except that listings A directory similar to a telephone directory except that listings

are by city and street address or by phone number rather are by city and street address or by phone number rather than alphabetical by last name.than alphabetical by last name.

• International ResearchInternational Research Availability of sampling frames varies dramatically Availability of sampling frames varies dramatically

around the world.around the world.


Sampling UnitsSampling Units

• Sampling UnitSampling Unit A single element or group of elements subject to A single element or group of elements subject to

selection in the sample.selection in the sample. Primary Sampling Unit (PSU)Primary Sampling Unit (PSU)

A unit selected in the first stage of sampling.A unit selected in the first stage of sampling.

Secondary Sampling UnitSecondary Sampling Unit A unit selected in the second stage of sampling.A unit selected in the second stage of sampling.

Tertiary Sampling UnitTertiary Sampling Unit A unit selected in the third stage of sampling.A unit selected in the third stage of sampling.


Random Sampling and Nonsampling Random Sampling and Nonsampling ErrorsErrors• Random Sampling ErrorRandom Sampling Error

The difference between the sample result and the The difference between the sample result and the result of a census conducted using identical result of a census conducted using identical procedures.procedures.

A statistical fluctuation that occurs because of chance A statistical fluctuation that occurs because of chance variations in the elements selected for a sample.variations in the elements selected for a sample.

• Systematic Sampling ErrorSystematic Sampling Error Systematic (nonsampling) error results from Systematic (nonsampling) error results from

nonsampling factors, primarily the nature of a study’s nonsampling factors, primarily the nature of a study’s design and the correctness of execution.design and the correctness of execution. It is It is not not due to chance fluctuation.due to chance fluctuation.


Random Sampling and Nonsampling Random Sampling and Nonsampling Errors (cont’d)Errors (cont’d)

• Less than Perfectly Representative SamplesLess than Perfectly Representative Samples Random sampling errors and systematic errors Random sampling errors and systematic errors

associated with the sampling process may combine to associated with the sampling process may combine to yield a sample that is less than perfectly yield a sample that is less than perfectly representative of the population.representative of the population.


EXHIBIT 16.EXHIBIT 16.44 Errors Associated with SamplingErrors Associated with Sampling


Probability versus Nonprobability Probability versus Nonprobability SamplingSampling• Probability SamplingProbability Sampling

A sampling technique in which every member of the A sampling technique in which every member of the population has a known, nonzero probability of population has a known, nonzero probability of selection.selection.

• Nonprobability SamplingNonprobability Sampling A sampling technique in which units of the sample are A sampling technique in which units of the sample are

selected on the basis of personal judgment or selected on the basis of personal judgment or convenience.convenience.

The probability of any particular member of the The probability of any particular member of the population being chosen is unknown.population being chosen is unknown.


Nonprobability SamplingNonprobability Sampling

• Convenience SamplingConvenience Sampling Obtaining those people or units that are most Obtaining those people or units that are most

conveniently available.conveniently available.

• Judgment (Purposive) SamplingJudgment (Purposive) Sampling An experienced individual selects the sample based An experienced individual selects the sample based

on personal judgment about some appropriate on personal judgment about some appropriate characteristic of the sample member.characteristic of the sample member.

• Quota SamplingQuota Sampling Ensures that various subgroups of a population will Ensures that various subgroups of a population will

be represented on pertinent characteristics to the be represented on pertinent characteristics to the exact extent that the investigator desires.exact extent that the investigator desires.


Nonprobability Sampling (cont’d)Nonprobability Sampling (cont’d)

• Possible Sources Of BiasPossible Sources Of Bias Respondents chosen because they were:Respondents chosen because they were:

Similar to interviewerSimilar to interviewer Easily foundEasily found Willing to be interviewedWilling to be interviewed Middle-classMiddle-class

• Advantages of Quota SamplingAdvantages of Quota Sampling Speed of data collectionSpeed of data collection Lower costsLower costs ConvenienceConvenience


Nonprobability Sampling (cont’d)Nonprobability Sampling (cont’d)

• Snowball SamplingSnowball Sampling A sampling procedure in which initial respondents are A sampling procedure in which initial respondents are

selected by probability methods and additional selected by probability methods and additional respondents are obtained from information provided respondents are obtained from information provided by the initial respondents.by the initial respondents.


Probability SamplingProbability Sampling

• Simple Random SamplingSimple Random Sampling Assures each element in the population of an equal Assures each element in the population of an equal

chance of being included in the sample.chance of being included in the sample.

• Systematic SamplingSystematic Sampling A starting point is selected by a random process and A starting point is selected by a random process and

then every then every nnth number on the list is selected.th number on the list is selected.

• Stratified SamplingStratified Sampling Simple random subsamples that are more or less Simple random subsamples that are more or less

equal on some characteristic are drawn from within equal on some characteristic are drawn from within each stratum of the population.each stratum of the population.


Proportional versus Disproportional Proportional versus Disproportional SamplingSampling• Proportional Stratified SampleProportional Stratified Sample

The number of sampling units drawn from each The number of sampling units drawn from each stratum is in proportion to the population size of that stratum is in proportion to the population size of that stratum.stratum.

• Disproportional Stratified SampleDisproportional Stratified Sample The sample size for each stratum is allocated The sample size for each stratum is allocated

according to analytical considerations.according to analytical considerations.


EXHIBIT 16.EXHIBIT 16.55 Disproportional Sampling: Hypothetical ExampleDisproportional Sampling: Hypothetical Example


Cluster SamplingCluster Sampling

• Cluster SamplingCluster Sampling An economically efficient sampling technique in which An economically efficient sampling technique in which

the primary sampling unit is not the individual element the primary sampling unit is not the individual element in the population but a large cluster of elements.in the population but a large cluster of elements.

Clusters are selected randomly.Clusters are selected randomly.


EXHIBIT 16.EXHIBIT 16.66 Examples of ClustersExamples of Clusters


Multistage Area SamplingMultistage Area Sampling

• Multistage Area SamplingMultistage Area Sampling Involves using a combination of two or more Involves using a combination of two or more

probability sampling techniques.probability sampling techniques. Typically, geographic areas are randomly selected in Typically, geographic areas are randomly selected in

progressively smaller (lower-population) units.progressively smaller (lower-population) units. Researchers may take as many steps as necessary to Researchers may take as many steps as necessary to

achieve a representative sample.achieve a representative sample. Progressively smaller geographic areas are chosen until a Progressively smaller geographic areas are chosen until a

single housing unit is selected for interviewing.single housing unit is selected for interviewing.


EXHIBIT 16.EXHIBIT 16.88 Geographic Hierarchy Inside Urbanized AreasGeographic Hierarchy Inside Urbanized Areas


What Is the Appropriate Sample What Is the Appropriate Sample Design?Design?

AppropriatAppropriate Sample e Sample DesignDesign

AppropriatAppropriate Sample e Sample DesignDesign

National vs. National vs. LocalLocal

National vs. National vs. LocalLocal

Knowledge of Knowledge of PopulationPopulation

Knowledge of Knowledge of PopulationPopulation TimeTimeTimeTime

ResourcesResourcesResourcesResources

Degree of Degree of AccuracyAccuracy

Degree of Degree of AccuracyAccuracy


EXHIBIT 16.EXHIBIT 16.99 Comparison of Sampling Techniques: Nonprobability SamplesComparison of Sampling Techniques: Nonprobability Samples


EXHIBIT 16.EXHIBIT 16.1010 Comparison of Sampling Techniques: Probability SamplesComparison of Sampling Techniques: Probability Samples

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