A researcher collects data on weekly study hours and exam scores for 200 students. The correlation coefficient is r = 0.72. A student argues that studying more causes higher scores because the correlation is strong. Which statistical concept most directly refutes this causal claim?
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A
Regression toward the mean — extreme scorers naturally move closer to the average on a second test regardless of study habits
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B
Confounding variables — a third factor such as prior academic ability may independently drive both study hours and scores
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C
Sampling variability — a sample of 200 is too small to detect a true population correlation
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D
The coefficient of determination — r² = 0.52 means 48% of score variance is unexplained, so the relationship is weak