We can no longer expect representative samples to accrue from random digit dial phone surveys, according to The Metrics Insider.
That’s a problem for those of us who rely on phone surveys to help define the audiences, issues and messages that are most likely to compel our coalitions members to coalesce and take action.
The full article is here; an excerpt follows:
“The CDC’s National Health Interview Survey has become a highly visible source in the research community for tracking the incidence of what they call wireless-only, and what media researchers generally call cell phone-only, households.
On Dec. 17, their latest findings were released, covering the first six months of 2008. According to the NHIS, 17.5% of US households were wireless only. To put that into perspective, just three years prior, in the same study, only 7.3% of US households were wireless-only.
When we look at target demographics, the cell-only situation becomes even more dramatic. Fully 21.6% of US Hispanics live in cell-only households. And consider this: 31.4% of 18-24 year-olds live in cell-only households, as do 35.7%– over a third!-of 25-29 year-olds…
Why is this a research issue? Well, most RDD is done at calling centers, using auto-dial systems that automatically place hundreds of calls, handing off the call to a live interviewer when someone answers. But it is against the law to auto-dial cell phones. So RDD sampling systematically and by design excludes cell phone exchanges. In order to sample cell phones, a human has to manually dial the number, rendering the process several times more costly than RDD dialing of land lines…
…we recruit our panelists exclusively online (save for our “Calibration sample,” a control sample that is recruited randomly and offline, but not via RDD.). This has many benefits, but for today’s purposes, it allows us to assure that we represent persons from all phone-status households.
A year ago we did a study of our U.S. panel, in order to understand both phone status composition of the panel, and how Web usage might vary by phone status. We found that 19% of our panelists were cell-only, and that another 23% were cell-primary; in other words, if we’d relied on RDD we would have totally excluded 19% of the panel, and dramatically under-represented another 23%.