Passage Summary: Hospitals started keeping track of mistakes, and then fewer patients got hurt; the author thinks the staff just started being more careful because they knew they were being watched.

Conclusion: The decrease in patient injuries was caused by staff becoming more meticulous due to the monitoring of their errors.

Reasoning: After hospitals started recording errors, the number of injuries caused by staff mistakes dropped significantly.

Analysis: The author is making a causal claim: monitoring caused the staff to be more careful, which in turn reduced injuries. To strengthen this, we need to bolster that causal link or rule out other possibilities. It turns out people tend to be a bit more careful when they know someone is checking their homework, but we need to be sure it wasn't just a coincidence. Look for an answer that shows the injury rate didn't drop at hospitals without this program, or one that confirms no other major safety changes were made at the same time.