Who you gonna call?
Keith Humphreys, an addiction researcher at Stanford, writes The newest Behavioral Risk Factors Surveillance System survey by the US CDC shows a substantially higher rate of binge drinking than in past surveys. BRFSS is the world’s largest telephone survey, and in 2009 they started calling cellphones for the first time.
Cellphone users, and especially those who don’t have any landline phone, are a lot younger on average than the rest of the population. That in itself need not be disastrous for surveys, since we know what proportion of the population is in each age group, and can rescale the numbers to remove the bias. The problem is that cellphone users also are different in other ways that are harder to measure, as the CDC’s experience shows.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »