By MEGAN THEE
Published: December 7, 2007
With more American households giving up their old-fashioned land lines and using cellphones for all calls, public opinion researchers are facing a challenge of how to make sure they are getting representative samples when conducting polls.
Since the 1970s, pollsters have relied on sampling techniques that depend on talking with people on their home land line telephones. For the most part, the polls sample the public by randomly dialing telephone numbers in every region from a list of area codes and exchanges known to be residences. The sample is weighted to the results of the latest census.
But cellphones are not geographically based, forcing pollsters to adjust their methods. In addition, a land line often represents a household and a cellphone often represents an individual.
More at the link
http://www.nytimes.com/2007/12/07/us/07polling.html?_r=1&ref=politics&oref=slogin