Which conclusion is supported by a flawed control selection in an ecological study of a coal plant's impact on lake pH?

Which conclusion is supported by a flawed control selection in an ecological study of a coal plant's impact on lake pH?

• A. The study would overestimate the plant's impact.
• B. The study would underestimate the plant's impact.
• C. The two lakes would have similar pH, masking the plant's impact.
• D. The geothermal lake would become neutral.

Answer: (C)

A flawed control can’t provide a clean baseline. If the control lake shares the same watershed characteristics, geology, and exposure to other acid sources as the lake near the coal plant, both bodies of water can end up with similar pH values regardless of whether the plant is acidifying the plant lake. That means any real acidification from the coal plant would be hard to detect, so the two lakes would appear to have similar pH, masking the plant’s impact. If the control somehow had a different baseline (more or less acidic for reasons unrelated to the plant), you could misstate the effect, but the key outcome of an improper control here is that the plant’s influence gets hidden because the baseline conditions are too similar.

A flawed control can’t provide a clean baseline. If the control lake shares the same watershed characteristics, geology, and exposure to other acid sources as the lake near the coal plant, both bodies of water can end up with similar pH values regardless of whether the plant is acidifying the plant lake. That means any real acidification from the coal plant would be hard to detect, so the two lakes would appear to have similar pH, masking the plant’s impact. If the control somehow had a different baseline (more or less acidic for reasons unrelated to the plant), you could misstate the effect, but the key outcome of an improper control here is that the plant’s influence gets hidden because the baseline conditions are too similar.