In a sampling question, compare the group a study wants to describe with the group that could receive the survey. Check whether the invitation list is connected to the opinion being measured; that connection can create selection bias, meaning some views are more likely to appear. A high response rate among invitees cannot include people who were left out.
Hints
- Hint 1
The target population is everyone the committee wants to describe, not only the people who answered. Who is the committee trying to describe, and could a student with no recent library checkout have received the poll?
- Hint 2
A representative sample should reflect the larger group rather than favor one kind of student. Recent library users may care more about library hours. How might that affect a poll about extending them?
Step-by-step
Compare the target group with the invitation list
Step 1Identify the group the estimate is for
No Desmos needed. This decision depends on who could receive the poll, not on arithmetic. The target population is the group the committee wants to describe: all students at the university. So an estimate for that group needs to account for students who haven't recently used the library.
- Step 2
Check who could receive the poll
The committee emailed only students who had checked out a book in the past month. A student who hadn't done that couldn't receive the poll, so the invitation list leaves out part of the target population.
- Step 3
Connect the invitation rule to the opinion
Recent borrowers may care more about library hours than other students and may be more likely to favor an extension. That's selection bias: the way students were chosen may tilt the answers away from what all students would say.
- Step 4
Limit what the result can claim
The describes the students who answered, not necessarily all students. Although of invitees responded, a high response rate cannot bring in students who were never invited. The result is likely biased because the poll included only recent library users. Choice C.