A social worker at a large high school wants to estimate the number of days students are absent. He randomly
selects 45 students and records the number of days each one is absent. The social worker constructs a 95%
confidence interval for the true mean number of days students at this school are absent. Which of the following
would decrease the margin of error?
O using a sample of size 30
O using a sample of size 40
constructing a 90% confidence interval
O constructing a 99% confidence interval