Apoll of american adults’ opinions about efforts to reform social security was conducted in 2004−2005 by the aarp, the nation’s largest organization for retired people. the poll results were criticized in some quarters because they included no respondents under the age of 30, even though voters aged 18 to 29 made up 17% of the 2004 electorate. by contrast, respondents aged 60 and above made up 34% of the sample but were only 24% of the electorate. this poll is most likely subject to which of the following types of bias?