medium · GRE Verbal

Researchers evaluating a reminder-message campaign observed that appointment attendance rose after reminders began. They concluded that the messages reduced missed appointments. The observation is suggestive, but the clinic simultaneously shortened waiting times; until that possibility is separated from the intervention, the causal interpretation remains provisional. Which statement can be inferred from the passage?

1. Every comparable investigation has found the same association
2. The identified alternative is certainly the sole cause of the observed change
3. The intervention is more effective than every competing policy not discussed in the passage
4. The observed change is compatible with the proposed explanation but does not by itself establish that explanation
5. The proposed intervention never produces the claimed effect in any population, even under conditions that eliminate the alternative identified by the author

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