Mobile Phones and Polling Accuracy
Since I have been posting a lot about mobile phones lately, I wanted to direct you towards a post from last year by Mark Blumenthal, aka Mystery Pollster. If you are interested in polling/statistics at all you should check him out regularly… Anyway, a lot of people have been wondering about the effect that wireless-only households will have on the accuracy of public opinion polling and Blumenthal weighs in with this:
We could calculate the “coverage error” that results from excluding wireless-only adults from political polls if we knew two things: (1) How the vote preferences of wireless only adults differ from those with working landlines and (2) the percentage of all likely voters with only wireless service. Unfortunately, both numbers are unknown.
Still, assume for the sake of argument that wireless adults are 5% of the electorate, that a survey of wired households shows a 48%-48% tie and that the missing wireless-only voters prefer John Kerry by a 20-point margin (58% to 38% - a pure but plausible guess based on the numbers for renters, low income, etc). If we were able to include the wireless only adults, it would change the overall preference by only one point - Kerry would lead 48.5% to 47.5%.
[snip]
Of course, that’s this year [2004]. Things could be very different next time. A recent study by the market research firm In-Stat/MDR estimates wireless only households growing to 30% in 2008. If that estimate holds, telephone polls will face enormous challenges in the very near future.
Seriously, go read the whole thing. And maybe this post too…