Mark Blumenthal | September 19, 2008
Topics: Cell Phones
We have followed the challenge posed to survey for the last four years, both here at Pollster and at its forerunner, my old blog MysteryPollster. Over the last four years, survey researchers have been developing techniques for interviewing respondents on their cell phone, and over the last few months, many of the well known national media surveys have been including samples of voters contacted on their cell phones in their national samples or conducting side-by-side tests. These include the Pew Research Center, Gallup (both the Gallup Daily and USA Today/Gallup surveys), CBS/New York Times, Time/SRBI and most recently NBC/Wall Street Journal, ABC/Washington Post and the new AP/GfK poll.
Over the last two weeks, some of these pollsters have provided updates on the impact of their cell phone samples (or lack thereof):
- ABC News polling director Gary Langer today describes their cell phone interviewing test in a new blog post today and describes the impact on the overall results as "negligible....The precise changes were 0 for Obama and -1 for McCain among registered voters, +0.7 for Obama and -0.8 for McCain among likely voters." These differences fell well within the survey's margin of error.
- NBC's First Read included this line in their recap of the latest NBC/WSJ poll: "[T]he poll included some cellphone surveys (we found no significant difference in cell phone respondents as we have from landline respondents." More details on the cell phone sample at the end of the filled-in questionnaire provided by the Wall Street Journal.
Keep in mind that these are relatively small scale tests, in which the margins of error for both the base land-line sample and the supplemental cell-phone test samples are probably larger than any likely effect. Gallup and the Pew Research Center have released similar tests based on larger samples that suggest a small benefit (perhaps 2 to 3 points on the margin) benefiting Barack Obama from the inclusion of cell phone only interviewing.
We will definitely have more to say on this subject in the weeks ahead. Those looking for all the gory details, on this subject may want to start with my series from last year on cell phones and political surveys (Part I and Part II).