We guard against this by using a combination or RBS and RDD sampling. However, it is nice to see the ABC News/Washington Post poll tested the approach, finding slight changes at most when cell-only respondents were included with a traditional land-line telephone sample.
Across 100 response categories the biggest difference was 2 points, which occurred in three cases. The rounded difference was 0 in 56 of the comparisons, and 1 point in 41.
During election season the ballot is of particular interest. Registered voters in the late August ABC poll split between Barack Obama and John McCain by 49-43 percent in the landline sample and 49-42 percent with cell-only respondents included. Among likely voters, it was 49-45 percent among landline respondents and 50-44 percent with cell-only respondents included.
Read the full ABC Blog post here.
