A 2022 study tested whether a phonics-focused curriculum improved reading scores. Researchers reported mean kindergarten reading scores in four districts that adopted phonics in different years, comparing scores 2 years before adoption to 2 years after: District P, 64 → 70; Q, 68 → 71; R, 60 → 75; S, 70 → 71. They also reported, for each district, scores in matched comparison districts that <em>never</em> adopted phonics, over the same windows: P-control, 65 → 68; Q-control, 67 → 70; R-control, 60 → 62; S-control, 71 → 73. The researchers argued the curriculum produced a real causal effect only in District R. The data most uniquely supporting this targeted claim is ______
Which choice most logically completes the text using the data above?
- Acheck_circle
the contrast in District R (gain of 15 points vs. control's 2-point gain) versus the other districts whose gains roughly matched their controls.
- B
District R's post-adoption score of 75.
- C
District P's gain of 6 points.
- D
the average gain across all four adoption districts.
Explanation
"Real causal effect only in District R" requires showing R's gain far exceeds its control while other districts' gains do not exceed theirs. Choice B captures this complete contrast across all four pairs, uniquely supporting the targeted claim.