OPRE504
Chaodong Han
OPRE504
Chapter Study Guide - Chapter 3 Surveys and Sampling
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I.
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Simple Random Sample (SRS)
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Sampling Methods
Every individual has an equal chance of selection within a sampling frame
Stratified Sampling (controlled random)
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Assign different weight of representation for each stratum
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Common characteristics within each stratum but differ across strata
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SRS in each stratum (gender, race, age, education level, etc.)
Cluster Sampling (controlled random)
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Split the population into similar parts or clusters and SRS across clusters
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The composition of each cluster is equally representative of the population
Multistage Sampling
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Use combination of stratified and cluster sampling as well as simple random samples
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Professional polling organizations and marketing research firms
Systematic Samples (simplified random)
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Pick a sample according to a systematic order (e.g., every 6th person exiting the poll)
II.
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Voluntary response bias
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When individuals choose on their own whether to participate in the sample;
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People with strong opinions tend to participate
Convenience sample bias
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Sample is easy for the researchers to obtain but may not be representative
Undercoverage bias
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Sampling Biases
When some portion of the population is not sampled at all or has a smaller
representation in the sample than it has in the population
Nonresponse bias
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A large fraction of those sampled fails to respond
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Those who respond differ from those who don’t
Response bias
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Respondents tailor answers to please the interviewer
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Survey questions are loaded with strong suggestions or preferences
Chaodong Han
OPRE504
Page 2 of 5
III.
An Example of Problematic Sampling Design
Background
Researchers wanted to know what fraction of the U.S. adults considers drinking and driving was a
serious problem.
They waited outside a bar they had randomly selected from a list of such establishments.
They stopped every 9th adult who came out of the bar and asked whether he or she thought drinking
and driving was a serious problem.
What is the population?

All bars
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All adults
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All adults in the bar
What is the population parameter of interest?
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The proportion of adults who drink and drive
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The proportion of adults who think drinking and driving is a serious problem
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The number of adults who came out of the bar
What is the sampling frame used in this study?
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Bar patrons
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All adults who drink
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All adults
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All bars
What is the sample for this study?
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All adults leaving the bar
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All adults who think drinking and driving is a problem
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Every 9th adult leaving the bar
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All adults
What sampling method was used?
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Voluntary sampling
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Convenience sampling
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Systematic sampling
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Stratified sampling
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Cluster sampling
Chaodong Han
OPRE504
Page 3 of 5
What type of bias is evident in this sample?
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Voluntary response bias
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Undercoverage and nonresponse bias
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Undercoverage and response bias
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Response bias
What problems might occur in generalizing the current sample to the population of interest ?
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Some people drink more than others
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Since those interviewed had just left a bar, they probably think drinking and driving is
less of a problem than do adults in general
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None
IV
An Example of Various Sampling Designs
In a public school system with 48 elementary schools, the school board is considering installation of
cameras in school public areas in order to deter bully and vandalism. The PTA wants to find out
whether parents agree with this proposal. List below are some of the ideas for gathering data.
Assume the schools are homogenous but differ from each other.
1. List the names of all the students alphabetically and contact the parents of every 25th student.
•
2.
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Cluster sampling
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Systematic sampling
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Convenience sampling
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Census
What kind of bias (if any) is most likely to occur?
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Response bias since the PTA wants parents to agree
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No evident bias if the sampling strategy is followed as described
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Undercoverage bias since the parents in the sample may not be representative of all
parents
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Voluntary response bias since only parents who feel strongly about the issue will
respond
Put a big ad in the newspaper asking people to log their opinions on the board web site.
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Convenience sampling
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Simple random sample
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Voluntary response sample
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Stratified sampling
Chaodong Han
OPRE504
Page 4 of 5

What bias if any is most likely to occur?
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Bias could result only if the strategy is not followed as described
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Undercoverage since only active parents involved with the PTA will be sampled
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Response bias since the PTA wants the parents to agree
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Voluntary response bias since only parents who feel strongly about the issue will
respond
3. Randomly select one of the grade levels and contact the parents of every student for the
grade.
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Cluster sampling
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Stratified sampling
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Voluntary response sample
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Simple random sample
What bias if any could occur?
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Undercoverage bias since only parents involved with the PTA will be sampled
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Undercoverage bias since the parents in the sample may not be representative of all
parents
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Response bias since the PTA wants parents to agree
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Bias could result only if the sampling strategy is not followed as described
4.
Mail a survey to the home of every student, and ask parents to fill it out and return it
within a week.

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Cluster sampling
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Voluntary response sample
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Attempt at a census
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Stratified sampling
What kind of bias (if any) could occur?
–
Undercoverage bias since the parents in the sample may not be representative
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Response bias since the PTA wants parents to agree
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Nonresponse bias since not all parents will respond
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Bias could result only if the sampling strategy is not followed as described
Chaodong Han
OPRE504
Page 5 of 5