Sites like SurveyJunkie and Swagbucks offer money in exchange for taking surveys, which doesn't always produce the best quality data. Researchers use online opt-in surveys all the time. Should they? Search around for ways to make a little extra money online, and you might find yourself at one of many sites that offer to pay you to take surveys. There's Swagbucks, SurveyJunkie, InboxDollars, and KashKick, for instance. On each of these sites, users are paid small amounts of money for completing surveys, playing games, or making purchases. The surveys on these sites are "opt-in" surveys, meaning that participants are actively choosing to take them, rather than researchers pulling a random sample of a population to poll, as professional pollsters do. Unsurprisingly, opt-in surveys can lead to some skewed results: Earlier this week, Pew Res...
