The dean of students at a large college is interested in learning about their opinions regarding the percentage of first-year students who should be given parking privileges in the main lot. He sends out an email survey to all
students about this issue. A large number of first-year students reply but very few sophomores, juniors, and
seniors reply. Based on the responses he receives, he constructs a 90% confidence interval for the true proportion
of students who believe first-year students should be given parking privileges in the main lot to be (0.71, 0.79).
Which of the following may have an impact on the confidence interval, but is not accounted for by the margin of
error?

response bias
nonresponse bias
sampling variation
undercoverage bias