In survey questions, selection bias means the way people enter a sample favors some members of the group over others. Compare the group the study wants to describe with who actually responded, then ask whether chance picked those people or they volunteered. A high response count cannot fix a sample drawn from a tilted source.
Hints
- Hint 1
A target population is the whole group an estimate is supposed to describe. Which teenagers does the magazine want its average to cover, and is that the same group as the website’s readers?
- Hint 2
A self-selected sample forms when people decide for themselves whether to answer. Readers had to visit this particular website and choose to respond. Could their social media habits differ from those of other teenagers?
- Hint 3
A large sample helps only if the way people enter it doesn’t favor one kind of person. Does getting more answers from the same website change who the poll reaches or who volunteers?
Step-by-step
Compare the intended group with the respondents
Step 1Identify the group the estimate is about
No Desmos needed. This question is about who the poll reaches, not a calculation. The magazine wants an average for teenagers throughout the country, so its target population, the whole group it wants to describe, is all teenagers in the country.
- Step 2
Identify who entered the poll
The poll appeared on a technology news website, and readers chose whether to answer. So the sample, the people who responded, consists of self-selected website readers, not teenagers picked by chance from across the country.
- Step 3
Check whether those readers represent all teenagers
Website readers may be more interested in technology than other teenagers, and those especially interested in the poll’s topic may be more likely to reply. Their social media time could differ from the countrywide average, so the respondents may not represent all teenagers.
- Step 4
Evaluate the method, not the response count
This is selection bias: the way people enter the poll may favor certain teenagers. Although responded, more responses from the same tilted source won’t correct how respondents were selected. The method is likely biased because it relies on self-selected readers of a technology news website. Choice B.