The next few questions are about dating relationships. This form of selection makes it possible to reach every American household with a telephone. Knowledge Networks employs a complex sample stratification design that incorporates the known probabilities of selection associated with geographical location, the number of phone lines, and whether or not the phone number is listed. Once a Knowledge Networks household is selected, members are contacted first by an express delivery mailing and then by telephone for enrollment in the Knowledge Networks TM Panel. Every participating Knowledge Networks household receives free hardware, free Internet access, free email accounts, and ongoing technical support.
Participants receive a short multimedia survey about once a week.
Surveys are delivered by email on the same standardized hardware, through the television set. 4.9 percentage points. Sampling error is only one form of potential error in public opinion surveys.