What does the migration to online polling mean for the country's trove of public opinion data gathered over the past four decades?
Pew Research Center conducts surveys over the phone and, increasingly, online. But these two formats don’t always produce identical results.
People polled by telephone are slightly less likely than those interviewed online to say their personal finances are in “poor shape."
The first video in Pew Research Center’s Methods 101 series helps explain random sampling – a concept that lies at the heart of all probability-based survey research – and why it’s important.