What are the strengths and weaknesses of polls?

Of course, not all polls have the same strengths and weaknesses.  Some polls are conducted better than others.  However, all polls at least share some potential strengths and weaknesses.

The main strength of polls is that they can tell us about the opinions of a large number of people without us having to ask every single person for their opinion.  Polls make use of scientific sampling techniques that allow them to interview a relatively few people and extrapolate the results to tell us what all the people in a population think.  This allows us to learn what all the people in our country (or in a state or other population) think on a variety of issues.  We would not be able to learn this if we always had to ask every member of a population for their opinion.

The major weakness of polls is that they do not always do a good job of telling us what people think.  One problem is that the poll questions might not give all the options that people want.  Let us say that a poll asks me whether I think that we should deport illegal immigrants.  The choices are yes or no.  What if I think that we should deport some illegal immigrants but not all of them?  In this case, the poll does not do a good job of capturing my opinion.  Typically, polls are weak at capturing opinions on nuanced issues that do not lend themselves to easy “yes or no” answers.

A second problem is that the wording of poll questions can influence people’s responses.  Imagine two poll questions that are meant to gauge opinion on the same issue.  One asks “Do you think the US should prevent all foreign Muslims from entering the country?”  The other says “Donald Trump has proposed banning all foreign Muslims from entering the country.  Do you agree with this policy?”  The second question might really end up measuring support for Trump rather than support for this particular policy.  Polls can be weak because they can often give skewed results due to problems in how questions are worded.

A third weakness is that people do not always tell pollsters what they really think.  Imagine that you are asked the above question about Muslims.  You believe we should exclude them, but you do not want to say so because you think that the pollster will disapprove of you if you voice such an opinion.  This can cause misleading poll results that are skewed in favor of socially acceptable answers.

A final weakness of polls today is related to technology.  Polls have long been conducted by calling people on their landline telephones.  Today, many Americans no longer have landlines and instead use cell phones only.  This means that polls that use only landlines might not be reaching a representative sample of Americans.