Bite Sized Thought Piece: Weighting Online Surveys
Most surveys conducted online use online access panels as a sample source. Results are then weighted to be representative of the population of interest. Weighting is the standard approach used to correct for the fact that those interviewed are not a perfect fit to that population.
When using the normal technique, usually called rim weighting, we assume that the variables used as targets account for the variation in statistics. Standard demographics and sometimes simple internet usage variables are used. For surveys involving population representation this can cause difficulties in producing results that are representative when comparing to offline sources.