In 2016, the Pew Research Center reported the results of a survey about public library usage. A nationally representative sample of 1601 people aged 16 and older who were living in the United States completed the survey. One survey question asked whether the survey respondent had visited, in person, a library or a bookmobile in the last year. A total of 768 of those surveyed answered "yes" to this question. Although the samples in national polls are not simple random samples, they are similar enough that our method gives approximately correct confidence intervals.

a. Explain in words what the parameter p is in this setting.

b. Use the poll results to give a 95% confidence interval for p.

c. Write a short explanation of your findings in part (b) for someone who knows no statistics.