An open online poll creates a voluntary-response sample: people decide whether to answer. To judge a claim about all residents, compare that group with the people who responded, then ask whether chance selected the respondents. A large response count cannot fix self-selection. People with strong opinions may be more likely to answer, so the respondents’ percentage may not describe the whole city.
Hints
- Hint 1
A sample is the group actually measured; the target population is everyone the council wants to describe. Which group does the reported percentage come from, and which group would a citywide claim describe?
- Hint 2
In a voluntary-response sample, people choose whether to answer, even if many people can see the link. Could residents with strong opinions be more likely to respond than residents who don’t care much?
Step-by-step
Check who chose the sample
Step 1Limit what the percentage describes
No Desmos needed. A calculator can’t tell you whether a poll represents a city. The target population is all city residents, the group the council wants to describe. Since of respondents favored the park, that percentage is known for the people who answered, not for everyone.
- Step 2
Check how people entered the poll
The council posted the poll rather than choosing residents by chance, so people decided for themselves whether to answer. Being able to see a poll is not the same as being chosen at random to answer it. Residents with strong views about the park may be more likely to respond.
- Step 3
Choose the claim the method supports
If residents with strong views respond more often, the sample could be biased, or tilted toward their views. May be biased names that possibility; it doesn’t claim bias definitely occurred. So this voluntary poll may not represent all city residents. Choice B.