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Public Opinion
• Public Opinion is the aggregation of people’ view
about issues, situations, and public figures.
• Why is Public Opinion important?
• Public opinion can shape public opinion by
providing policymakers with information.
– Provides outlet for citizen voice in Representative
• Should elected officials pay attention to
– Trustee vs Delegate Models of Representation
Trends in Opinion
The Economy and the 2008 Election
Presidential Approval Ratings
Healthcare Reform Attitudes in NM
What is your opinion regarding the current state of health care in New
Fine as
Com ple te ly
Re built
M inor
Change s
M ajor Change s
Measuring Public Opinion- Sampling
• Public opinion polls are the primary tool used to
assess how the public feels about particular issues,
and is a critical tool for elected officials.
• Because you cannot ask the entire public questions
about any particular issue, pollsters must rely on
– Target Population : Group of people inferences will
be drawn from.
– Sample Population : Part of the target population
selected for analysis.
• Public opinion is unfortunately often inconsistent at
the individual level, which raises questions about the
validity of attitudes.
• However, at the aggregate level attitudes seem to be
rather stable.
The Scientific Approach to Polling
• There is a scientific method used to ensure that
a survey is not biased.
• When samples mirror the population they are
said to be “Representative”.
• Randomness is critical to sampling.
– Randomness implies that each person within the
entire population being polled has an equal chance of
being chosen.
Inferences about the Population
• Values calculated from samples are used to
make conclusions (inferences) about unknown
values in the population
• Variability
– different samples from the same population may yield
different results for a particular value of interest
– estimates from random samples will be closer to the
true values in the population.
– how close the estimates will likely be to the true values
can be calculated -- this is called the margin of error
(usually +/- 3%) : The larger the sample size the
smaller the sampling error (probability and rule of
large numbers).
Sources of Selection Bias
• Selection Bias is bad because it
systematically favors certain outcomes
based on who is asked to participate.
• Voluntary response sampling
– allowing individuals to choose to be in the sample
– Classic example is setting up a table in SUB
• Convenience sampling
– selecting individuals that are easiest to reach
– often used for tough to reach groups (Dreamers,
– Both of these techniques are biased
– systematically favor certain outcomes
Simple Random Sampling
• Each individual in the population has the same
chance of being chosen for the sample
• Each group of individuals (in the population) of
the required size (n) has the same chance of
being the sample actually selected
• Random selection:
– “drawing names out of a hat”
– table of random digits
– computer software - CATTI System
Probability Sample
• A sample chosen by chance
• Must know what samples are possible and
what chance, or probability, each possible
sample has of being selected
• A SRS gives each member of the
population an equal chance to be selected
Cautions about Sample Surveys
• The following are all examples of measurement
error, or the error that arises from attempting to
measure something as subjective as opinion
• Undercoverage
– some individuals or groups in the population are left
out of the process of choosing the sample
• Nonresponse
– individuals chosen for the sample cannot be contacted
or refuse to cooperate/respond
• Response bias
– behavior of respondent or interviewer may lead to
inaccurate answers or measurements
• Wording of questions
– confusing or leading (biased) questions; words with
different meanings
Undercoverage and Non-Response Bias
• Doing internet surveys have become
very popular due to costs and easy
– How might this approach lead to
• High non-response rates among
particular populations can also be a
Response Bias
Asking the Uninformed
Washington Post National Weekly Edition (April 10-16, 1995, p. 36)
• A 1978 poll done in Cincinnati asked
people whether they “favored or
opposed repealing the 1975 Public
Affairs Act.”
– There was no such act!
– About one third of those asked expressed
an opinion about it.
Response Bias
Interviewer Effect
• Can you think of any ways in which
people may be influenced by the people
actually conducting the interview?
• Some examples include:
– Race and Gender of interviewer
– Facial Expressions to answers given
Wording of Questions
• Questions should be simple and nonbiased in nature. They should not have
different meanings.
• Here is an example of a biased question:
– If you found a wallet with $20 in it, would you
do the right thing and return the money?
– If you found a wallet with $20 in it, would you
return the money?
• You must also be cautious of “loaded”
terms such as welfare or illegal immigrant.
Order of Questions
• How often do you normally go out on a
date? About _ times a month?
• Why is asking the following question right
after this one a problem?
• How happy are you with life in general?
Polling Issues Facing 2008 Election
• The “Bradley Effect”
– Potential over-estimation of Obama vote
due to social desirability.
• The inability of most polls to capture
first time voters, particularly the youth
• What do you think, can we trust the
• What are our alternatives?
The Socialization Process
• Political socialization is the process of acquiring
political attitudes that begins at childhood.
• Family has been most critical soc. agent
– Children usually have the same party preference as
their parents, especially when both parents have the
same party identification.
• Has changes in family structure decreased
impact of family in socialization process?
• What is the role of Education in Socialization?
– Learn the “rules of the game” in politics
– Exposed to different people and views
– Increases general awareness and knowledge of
political issues
Are Schools Socializing Anymore?
• Many argue that schools are not doing a good job
of providing basic political concepts to students.
• Perception vs. Reality (Studies of HS Students)
– More than 50% did not know # of US senators
– Over 60% could not name three branches of
– One third did not know that the first ten
amendments are the bill of rights.
• Recent studies suggest things might even get
worse in college!
• What are your thoughts?
• What is the Media’s role in Public Opinion?
• Most Americans get their political
information from TV, leading many to call
the Media the 4th branch of government.
• Recent surveys of high school students
indicate that television is more important in
political socialization than family or school.
• Others contend that media is not as
powerful as we think because everyone
has pre-conceived opinions.
• How significant is the media in
• Socioeconomic Status Differences
– How does income influence public
• The wealthy are more likely to be
conservative, and less likely to support
government aid programs. However,
education tends to lead to more liberal
views on policies.
• There are also significant differences in
public opinion by Race, Gender, and
Religious affiliation.