A radio show invites listeners to call in their views on a tax proposal. The biggest threat to validity here is
- A
Sampling error from too small a sample
- B
Random measurement error
- Ccheck_circle
Voluntary-response bias — opinionated listeners self-select
- D
Confounding by tax bracket
Explanation
Voluntary-response samples overrepresent strongly opinionated individuals. No randomization → systematic bias, not just sampling variability.