"For years, people have contended that a right-leaning bias exists in public opinion polls that fail to consider cell phone users. This argument has some new backing-- a Pew Research Center report released Monday suggests that polls based on landline-only samples do, in fact, suffer from a Republican bias.
The report, which confirms findings from a mid-October study, suggests that support for Republican candidates is significantly higher when a survey's sample is composed only of landline telephone respondents, rather than both landline and cell phone users ("dual frame samples"). Pew calculates a bias among likely voters in 2010 that is about twice as large as the statistical skew evident in 2008 landline-only election surveys."
TPM - Pew Study Finds Republican Bias In Landline-Only Polls
"The number of Americans who rely solely or mostly on a cell phone has been growing for several years, posing an increasing likelihood that public opinion polls conducted only by landline telephone will be biased. A new analysis of Pew Research Center pre-election surveys conducted this year finds that support for Republican candidates was significantly higher in samples based only on landlines than in dual frame samples that combined landline and cell phone interviews. The difference in the margin among likely voters this year is about twice as large as in 2008
Across three Pew Research polls conducted in fall 2010 -- conducted among 5,216 likely voters, including 1,712 interviewed on cell phones -- the GOP held a lead that was on average 5.1 percentage points larger in the landline sample than in the combined landline and cell phone sample.
In six polls conducted in the fall of 2008, Barack Obama's lead over John McCain was on average 2.4 percentage points smaller in the landline samples than in the combined samples"
The Growing Gap between Landline and Dual Frame Election Polls
Republican Vote Share Bigger in Landline-Only Surveys
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