Andrew Mercer

We examine how an opt-in poll may have unintentionally misled the public about the sensitive issue of Holocaust denial among young Americans.

Pew Research Center conducted a study to compare the accuracy of six online surveys of U.S. adults – three from probability-based panels and three from opt-in sources. On average, the absolute error on opt-in samples was about twice that of probability-based panels.

National polls like the Center’s come within a few percentage points, on average, of benchmarks from high response rate federal surveys.

While the growth of online interviewing is a prominent trend in polling, there is variation within that trend in how researchers recruit respondents. This study finds that sourcing affects data quality.

About a quarter of all officers say they have ever fired their service weapon while on the job. Are some more likely than others to have fired their weapon in the line of duty?

Majorities of police officers say that recent high-profile encounters between black citizens and police have made their jobs riskier and left many officers reluctant to fully carry out some of their duties.

There is a great deal of speculation but no clear answers as to the cause of the disconnect, but there is one point of agreement: Across the board, polls underestimated Trump's level of support.

As oversampling and its possible effect on presidential polls are spotlighted ahead of Election Day, learn more about this practice and how pollsters adjust for it.

Some of the better-known statistical rules of thumb that a smart consumer might think apply in polls are more nuanced than they seem. In other words, as is so often the case in life, it’s complicated.