An inference question about a study tests what you can conclude from the groups compared. Read what changed during the study, then name each group and what it showed. If several things changed together, the result alone can't separate their effects. Predict a cautious conclusion that fits every group, keeping what the study can show separate from what it can't. Answers often go too far by naming a cause the study hasn't proved.
Hints
- Hint 1
List all the safety measures the city introduced. How did the timing of those changes overlap?
- Hint 2
Look at the comparison between intersections in the research team's sentence. What did those intersections share, and how did collisions change in each group?
Step-by-step
Compare the intersections, then limit the claim
Step 1Track all the changes
The officials point to a citywide 18% drop after adding markings, and the blank asks what the research team can conclude from that evidence. What else changed over the same period? The city lowered the default speed limit and added speed cameras on major corridors, so several changes happened together and each could have affected collisions.
- Step 2
Find what the comparison can show
Did collisions also fall where there were no new markings? Intersections without new markings but located on corridors with cameras had declines similar to those with new markings. Many marked intersections were also on camera corridors, and a decline occurred without new markings too. The comparison weakens the claim that markings alone explain the drop, without showing that markings had no benefit. It also can't tell how much the cameras and the lower speed limit each helped, since both changes happened during this period.
- Step 3
Keep the conclusion within the evidence
The phrases the main reason and best explains each say which cause mattered most, but the comparison doesn't rank cameras, markings, and the lower speed limit. Does only at intersections follow from the study? No, because it never compares marked intersections with and without cameras. The phrase cannot be credited as the sole cause leaves room for more than one cause without denying that markings may have helped. Choice B.