1,961 U.S. adults (aged 18 and over). Figures for age, sex, race, education, region and household income were weighted where necessary to bring them into line with their actual proportions in the population. Propensity score weighting was also used to adjust for respondents’ propensity to be online.
In theory, with probability samples of this size, one could say with 95 percent certainty that the overall results have a sampling error of plus or minus 2 percentage points of what they would be if the entire U.S. adult population had been polled with complete accuracy. Unfortunately, there are several other possible sources of error in all polls or surveys that are probably more serious than theoretical calculations of sampling error. They include refusals to be interviewed (nonresponse), question wording and question order, and weighting. It is impossible to quantify the errors that may result from these factors. This online sample was not a probability sample.