A wildlife researcher weighed all the raccoons that were trapped in suburban neighborhoods before they were released back into the wild. The researcher used this data to conclude that the raccoons in the state were getting heavier. What error did the researcher make?

The researcher weighed only raccoons trapped in suburban neighborhoods, so the sample may not represent raccoons across the entire state. Suburban raccoons could differ in weight from raccoons living elsewhere, making the conclusion that all state raccoons were getting heavier unreliable. The correct choice is A: the sample is biased because it included only suburban-trapped raccoons.

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