21.13 Using public libraries. The Pew Research Center Libraries 2015 Survey examined the attitudes and behaviors of a nationally representative sample of 2004 people ages 16 and older who were living in the United States. One survey question asked whether the survey respondent had visited, in person, a library or a bookmobile in the last year. A total of 922 of those surveyed answered Yes to this question. Although the samples in national polls are not SRSs, they are similar enough that our method gives approximately correct confidence intervals.