have long been interested in the moods and opinions of the people.
After all, members of Congress and the President are elected to represent
the people, a difficult task if one does not know and understand what
the people want. Even George Washington employed his own "pollster," a
friend back in Virginia who would mingle with the "ordinary folks" to
find out what they thought of the President.1 While
the measurement of public opinion has become much more scientific and
precise since Washington's day, the attitudes of the public have always
played an important role in shaping public policy and the direction
of the nation.
What is Public Opinion?
opinion" is the distribution of opinions and attitudes held by the
public. Individuals hold a wide variety of opinions. By measuring these
opinions at the individual level and aggregating them, the proportions
of the population with particular beliefs and preferences can be determined.
When measuring public opinion, pollsters are not only concerned with
the content of public opinion, i.e. what it is that people think and
believe, but also with the stability of people's opinions over time.
It is also useful to know how strongly the public holds particular
opinions and the direction those opinions seem to be moving. The content,
stability, intensity and direction of public opinion are all important
indicators of what the public wants and expects out of its government
and political leaders. While popular opinion is not the only factor
that determines public policy, it is generally the most important one.
The role of public opinion in a representative democracy is further
opinion is not measured by asking every individual in the population
questions about his or her opinions. In a nation of 270 million people,
doing so would be impossible. Instead, pollsters ask a small group
of individuals a set of questions and then generalize from their findings
about that group to the larger population. Choosing a group of individuals
out of a population that is representative of the entire population
and then accurately measuring the opinions of those individuals is
technical and complex.
group of people selected out of a population to be asked questions
on a survey is called a "sample." For the results of a survey to be
accurate, the sample must be similar to the broader population in terms
of race, age, sex, education, income and other important characteristics.
If the sample is not representative of the population, the opinions
of those in the sample cannot be generalized to the larger group.
big does a sample need to be? The answer might surprise you. First,
sample size depends much more on the amount of diversity in a population
than it does the size of that population. For example, if every individual
in a one million person population holds the exact same opinions, a
sample size of one would be sufficient to accurately gauge the opinions
of the group. In contrast, if every person in a group of one thousand
people held very different opinions on a subject or subjects, a sample
size of one thousand might be required to accurately measure the group's
attitudes. (Technically, if every member of a population is surveyed,
there is no "sample" or "sampling" involved, just the population.)
A sample must be large enough, then, to reflect all of the significant
variations in opinions and attitudes throughout the population. So
how big is big enough? For small populations, say of five hundred or
less, a researcher is generally better off simply surveying the entire
group. In contrast, a sample of five hundred is generally sufficient
to measure the opinions of a population of 100,000 people. In fact,
as population size increases, the proportion of a population required
to comprise an acceptable sample decreases. Repeated experimentation
with varying sample sizes and extensive statistical and probability
analysis has led to the conclusion that a relatively small, randomly
drawn sample of 1,200 or 1,500 individuals can be highly representative
of a population of more than 250 million people. In fact, increasing
sample sizes to 5,000 or even 100,000 does not substantially improve
the accuracy of the results.
In theory, selecting a random sample is straightforward. First, a researcher
must decide what group of people he or she is interested in learning about.
For example, if someone is interested in predicting how people will vote
in an upcoming election, the relevant population consists of those individuals
who are going to vote. Similarly, if one wants to measure the opinions
of homeowners, the population consists of people who own homes. Once a
population is defined, the next task is to select a representative sample.
The most effective way to do this is to randomly select individuals from
a list of every individual in the population. In most cases, however, it
is difficult or impossible to obtain a list of everyone in the relevant
population. For instance, in the previous voting example, the list of those
who actually vote will not be determined until election day. In such cases,
researchers must do their best to randomly select people who are highly
likely to be in the population.
In practice, most public opinion surveys
are conducted by telephone. Using specialized computer software, random
telephone numbers are dialed and interviewers attempt to complete interviews
with persons in those households. To promote the randomness of the sampling
process, interviewers may also be instructed by the computer program
to ask for either a male or female respondent. Another less-frequently
used sampling technique involves randomly selecting addresses in a neighborhood
or area and then having interviewers personally visit the homes at those
addresses. A more commonly used but more problematic technique is to
mail surveys to randomly selected individuals or households.
Despite some early setbacks (see the box on sampling above), pollsters
have become very skilled at drawing representative samples. However, the
single most difficult sampling problem is not drawing a representative
sample, but rather securing completed interviews with each selected individual.
For a variety of reasons, many of the people selected to be in a sample
will not answer the questions on a survey--they may be too busy, too disinterested,
or they may simply be unavailable. If the people who refuse to complete
the survey share similar characteristics, such as working at the same time
of day or having similarly hostile attitudes toward public opinion surveys,
their absence from the sample will diminish the survey's generalizability.
Unless all kinds of people are included in the sample, even those who don't
like to answer surveys, the sample will not be a representative cross-section
of the entire population.
Assuming that every member of a random sample is willing and available
to answer the questions on a survey, pollsters must still design valid
and reliable questions and then ask them of each individual in the sample.
If the questions that are asked are not carefully written and presented
consistently, the results may be inaccurate even with a good sample. Several
problems associated with survey questionnaire design and interviewing must
be anticipated and accounted for to make the results as accurate as possible.
Pollsters must exercise caution in writing questions because the way a
question is worded can influence how individuals respond to it. Leading
questions, loaded phrases, poorly worded questions, providing responses
is a particular order or even the order in which questions are asked can
all effect the responses that are given.
For example, if a researcher was interested in measuring public support
for a state governor or member of Congress, he or she might simply ask: "Do
you approve or disapprove of the way [insert the politician's name] is
handling his/her job as [insert title of office]?" Altering this question
in any way might change the results of the survey. Pollsters have discovered
that even including titles such as "Governor," "Senator," "Congressman," or "President" tends
to slightly increase the approval ratings of politicians. Using descriptive
words, such as "successful" or "hard-working," can
alter the results even more. Asking the question as it stands immediately
after asking a question that casts the individual in potentially positive
or negative light can also alter individual responses. For example, if
a researcher asked respondents what they would think of a politician if
they found out he or she was having an affair and then asked the "approve
or disapprove" question, the results would be less favorable for the
politician than if the question had been asked in isolation.
The accuracy of individual responses to survey questions can also be influenced
by unwillingness (because of evasiveness) or inability (because of a lack
of information or poor memory) to answer questions accurately. Respondents
may also give "socially desirable" answers instead of accurate
ones when asked about such positively viewed activities as voting or donating
to charities or negatively viewed activities such as criminal behavior
or discrimination. The appearance and tone of voice of the interviewer
can also influence the way people respond to survey questions.
How to Read Poll Information
Despite all of the difficulties associated with accurately measuring public
opinion, skilled and conscientious survey researchers are still able to
conduct public opinion polls that yield valid and reliable results. As
a consumer of the news and of public opinion polls, you should, however,
look at public opinion poll results with a critical eye. Was the sample
selected randomly? What was the response rate of individuals in the sample?
What kinds of questions were asked? In what order?
In most cases, you will not be provided with enough information to answer
all of these questions. A growing number of news outlets, however, are
using the Internet to disseminate detailed information about the surveys
they conduct, often publishing the entire survey questionnaire online for
readers to see for themselves. In almost every case though, what is reported
about a poll is the sample size, the dates the poll was conducted and the "margin
of error" for the poll.
A poll's "margin of error" is a statistical statement of the
amount of confidence the survey researcher has in the results of his or
her poll. Most public opinion polls have a margin of error between plus
or minus seven and plus or minus three percentage points. What this means
is that the percentages of individuals in the sample who chose each response
to any given question could be off either direction by the magnitude of
the reported margin of error.
the example to the right, the results of Survey A show that Candidate
Fred is supported by 55% of the voters while Candidate Wilma is supported
by 45%. The margin of error for Survey A is plus or minus 5%. This
means that each candidate's support could be as much as five percentage
points higher or lower in the population than it was measured in the
sample. In this case, adding five points to Candidate Wilma's total
and correspondingly subtracting five points from Candidate Fred's would
put each candidate's support at 50%. Survey B, taken a month after
Survey A, shows that Candidate Wilma is now supported by 60% of the
voters while Candidate Fred has dropped to 40%. With a margin of error
of plus or minus 4%, the lowest Wilma's support in the population is
likely to be is 56%, while Fred's likely high is 44%. Even adjusting
for the margin of error in Survey B, Wilma enjoys a clear lead over
Fred. Based only on the results of Survey A, however, the race is too
close to call because the difference between the two candidates is
within the margin of error.
Public Opinion and Democracy
was noted at the outset, public opinion has always been an important
influence in American politics. Indeed, even the Federalists sought
to build public support for the Constitution during the debates on
ratification so the delegates to state ratifying conventions would
feel compelled to cast votes in support of the document. That is not
to say, however, that the Federalists trusted the opinions of the people.
On the contrary, the representative system created by the Constitution
reflects their fears about government by majority opinion. In particular,
the Senate, with its members originally chosen by state legislators,
not directly by the people, was designed to insulate public policy
decisions from the opinions of the people. Indeed, James Madison declared
in The Federalist No.
Senate] may be sometimes necessary as a defense to the people against
their own temporary errors and delusions. As the cool and deliberate
sense of the community ought, in all governments, and actually
will, in all free governments, ultimately prevail over the views
of its rulers; so there are particular moments in public affairs
when the people, stimulated by some irregular passion, or some
illicit advantage, or misled by the artful misrepresentations of
interested men, may call for measures which they themselves will
afterwards be the most ready to lament and condemn. In these critical
moments, how salutary will be the interference of some temperate
and respectable body of citizens, in order to check the misguided
career, and to suspend the blow meditated by the people against
themselves, until reason, justice, and truth can regain their authority
over the public mind?
no uncertain terms, the Framers of the Constitution anticipated that the
opinions of the people would influence the decisions made by political leaders,
but they also hoped that the representatives of the people would not simply
mimic the passions of the majority at any given moment. Indeed, the process
of representation, as it is practiced by most members of Congress, is a much
more careful and considered exercise than reading opinion polls and voting
accordingly (see "Congressional Representation").
the opinions of the people be trusted? An abundance of survey evidence
suggests that the people, on the whole, display an astonishing lack
of information about the political system, its processes and about
particular policy problems and issues. If public opinion is so poorly
informed, would it not be easily manipulated? That is at least one
reason the Framers favored republican, i.e. representative, government
over democracy. By requiring the representatives of the people to periodically
face reelection, they provided a mechanism for keeping them accountable
for their decisions. In between elections, however, members of Congress
could cast votes in Washington and then go back home and explain them.
In a republic, there are bound to be differences of opinion between
the people and their elected representatives. The Framers appear to
have hoped such differences would arise regularly. When such differences
exist, though, it is the responsibility of each representative to explain
to the people back home why he or she has cast a vote that was contrary
to the will of the people. If the explanation is inadequate or unconvincing,
the people can choose to send a new representative to Washington.