A study compared four schools' science test scores along with two factors: lab-equipment quality (high/low) and class size (small/large): School A, high equip + small class, 84; B, high equip + large class, 76; C, low equip + small class, 78; D, low equip + large class, 68. The researchers argued that <em>both</em> equipment and class size independently affect test performance. The strongest support for class size's <em>independent</em> role is ______
Which choice most logically completes the text using the data above?
- A
School A's score of 84.
- B
School D's score of 68.
- C
the gap between A and D.
- Dcheck_circle
the comparison A vs. B (both high equip: 84 vs. 76, an 8-point gap) and C vs. D (both low equip: 78 vs. 68, a 10-point gap)—class size shifts scores independently of equipment level.
Explanation
To show class size has an independent effect, hold equipment constant and vary class size. Choice B does this in both equipment strata, showing class size shifts scores by 8-10 points regardless.