Chapter 37: Measuring Public Opinion
CLEP American Government, Chapter 37
Measuring Public Opinion
A neighborhood website asks visitors whether the city should close a downtown street to cars. More than 40,000 people respond, and 76 percent favor the plan. A probability survey of 1,000 city residents finds 48 percent support. The website has far more answers. The survey may still provide the better estimate because a count becomes evidence about a public only when the people counted are connected to that public by a credible design.
Scientific polling
A scientific poll starts with a clearly defined population and a method that gives researchers a defensible basis for generalizing from a sample. The population might be all adults in a state, registered voters, or likely primary voters. Those groups are not interchangeable. Before reading a percentage, ask exactly whom the poll claims to describe.
Population and samples
In polling, the population is the full group a researcher wants to understand. A sample is the smaller group selected for observation. If the question concerns eligible voters in Ohio, adults nationwide are the wrong population and people who happen to visit a campaign website are a poor substitute for a sample. Clear labels prevent a statistic from quietly changing its meaning.
Random sampling
Random sampling is a probability procedure, not a casual choice of whoever is nearby. Each unit covered by the sampling frame has a known chance of selection. Researchers might randomly select addresses, telephone numbers, precincts, or people within households. Random selection helps prevent the researcher's preferences from deciding who enters the sample.
Representative samples
A representative sample supports accurate conclusions about its target population. It is not simply a miniature group that looks demographically similar at first glance. Researchers must consider who was covered, who could be selected, who responded, how the questions worked, and whether weighting corrected known imbalances without creating new instability.
Sampling error
Even a well-selected probability sample will not reproduce the population perfectly. Sampling error is the chance difference that arises because researchers observe some members rather than everyone. If the same design drew many samples, the estimates would vary around the population value. Larger effective samples usually reduce that variation. Under a simple random design, quadrupling the sample size roughly halves the standard error; the size of a large population matters much less.
Margin of error
Even a well-selected probability sample will not reproduce the population perfectly. Sampling error is the chance difference that arises because researchers observe some members rather than everyone. If the same design drew many samples, the estimates would vary around the population value. Larger effective samples usually reduce that variation. Under a simple random design, quadrupling the sample size roughly halves the standard error; the size of a large population matters much less.
Question wording
A respondent answers the question placed in front of her, not an abstract idea floating outside the interview. Leading wording signals a preferred response. Loaded wording attaches praise or blame. Vague language leaves the policy undefined, and a double-barreled question joins two matters that a person may judge differently. "Do you support the responsible reform?" carries approval into the item. "Should the city cut taxes and expand parks?" cannot show what a resident thinks if she favors one action and rejects the other.
Question order
A respondent answers the question placed in front of her, not an abstract idea floating outside the interview. Leading wording signals a preferred response. Loaded wording attaches praise or blame. Vague language leaves the policy undefined, and a double-barreled question joins two matters that a person may judge differently. "Do you support the responsible reform?" carries approval into the item.
Response bias
A respondent answers the question placed in front of her, not an abstract idea floating outside the interview. Leading wording signals a preferred response. Loaded wording attaches praise or blame.
Nonresponse bias
Nonresponse bias can occur when people selected for a survey do not participate and the nonrespondents differ from respondents in a way related to the result. The problem is not simply that the final sample is smaller. It is that the people whose answers are missing may have answered differently from those who completed the interview.
Push polls
A push poll is persuasive campaign communication disguised as research. It typically reaches many people, delivers damaging or suggestive claims, and seeks attitude change rather than a defensible population estimate. A legitimate message test may expose a sample to arguments, collect outcomes, and disclose the design. Purpose, scale, transparency, and actual analysis distinguish the experiment from mass advocacy wearing the appearance of a poll.
Exit polls
An exit poll samples people after they vote. It can estimate how participating groups voted and which issues they report considering. Its design must cover precincts, voting times, early and mail ballots, languages, and refusals. Exit polls are estimates, not official ballot counts, and they describe voters reached by the design rather than nonvoters or all eligible citizens.
Tracking polls
It can estimate how participating groups voted and which issues they report considering. Its design must cover precincts, voting times, early and mail ballots, languages, and refusals. Exit polls are estimates, not official ballot counts, and they describe voters reached by the design rather than nonvoters or all eligible citizens.
Interpreting charts, graphs, and polling data
A movement that follows a debate may be real, but timing alone does not isolate the debate from news, sample turnover, or altered procedures. Comparable repeated measures and uncertainty provide a stronger basis for interpretation.
Survey mode, weighting, and panel designs
Survey mode is the way answers are collected, such as telephone, web, mail, text, or face-to-face interviewing. Mode can change who is reachable and how people answer. An interviewer may increase social-pressure effects, while a web form can display a long list that would be difficult to remember by telephone. A change in mode can therefore interrupt a trend even when the wording stays similar.
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