Which of the following is not a voluntary response sample?

• A. A radio show asks listeners to call in if they have an opinion on a topic.
• B. An online poll where anyone can choose to participate is conducted.
• C. A researcher randomly selects $100$ students from a university roster to participate in a survey.
• D. A newspaper invites readers to submit their views on a recent event.

Answer: (C)

Verified step by step guidance

1. Understand the definition of a voluntary response sample: it is a sampling method where participants choose themselves whether to participate, often leading to bias because only those with strong opinions tend to respond.
2. Examine each option to identify if participants self-select or are chosen by the researcher:
3. Option 1: A radio show asks listeners to call in if they have an opinion. Here, participants choose to respond, so this is a voluntary response sample.
4. Option 2: An online poll where anyone can participate is also voluntary because people decide on their own to take part.
5. Option 3: A researcher randomly selects 100 students from a university roster. Since participants are randomly chosen rather than self-selected, this is NOT a voluntary response sample.