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Thinking about Elections

Pondering Opinion Polls
By Juliet Zavon
Posted: 2024-02-22T05:00:00Z

WHAT POLLS DON’T TELL YOU -- In an era when people no longer answer all phone calls, conducting a good poll is increasingly problematic (and costly.) So, how can you judge the accuracy of polling data? First, no single poll is accurate. An average of polls is more meaningful. Before accepting reporting about a poll consider:

+ Who was polled - Polls attempt to reflect public opinion by using a random sample of representative people, but poll results will be different depending on who was polled—all adults? registered voters? likely voters? Each “group” yields a different result and introduces different statistical “noise” that moves it away from a random sample. 

+ Was the poll conducted by robo-call, live interview, online? It’s hard to reach people on the phone, let alone reach a representative sample of respondents. As for internet polls, respondents are self-selecting, not “random.”

+ Look for the error margin when poll results are reported. A poll with a sample size of 400 people has a margin of error of +/- 4.9 percentage points. If that poll reports 45%, it is actually 45%, +/- 4.9. That’s a big range. A sample size of 800 has a margin of error of +/- 3.5 percentage points. The margin of error rapidly increases as you drop below 400 respondents and decreases slowly above 1200 respondents (which has an error margin of +/-2.8.)

+ Consider the media’s motives when reporting on polls. Conservative and liberal media are more likely to report results favorable to their candidates. Even nonpartisan media know that “New Poll Shows Race Hasn’t Changed” isn’t a great headline. Also, a media company that sponsors a poll is likely to want to hype their own findings.

The Quinnipiac Poll is well regarded. Read what they say about their methodology at the link.