A study comparing articaine with lidocaine reports RR = 3.1 with a 95% confidence interval of 3.4 – 4.7 and p = 0.001. What does this tell you about efficacy?

Correct answer: C. Articaine is more effective than lidocaine, and the result is statistically significant

• A. Equivalence would require the confidence interval to CONTAIN 1. It does not.
• B. An RR above 1 favours the exposure group (articaine). An RR below 1 would have favoured lidocaine.
• C. CORRECT. A RELATIVE RISK ABOVE 1 means the outcome is more likely in the articaine group; RR = 3.1 indicates roughly three times the likelihood of successful anaesthesia. The confidence interval EXCLUDES 1, and p = 0.001 is below the conventional 0.05 threshold — so the result is STATISTICALLY SIGNIFICANT and favours articaine for the outcome measured.
• D. The relative risk described concerns the EFFICACY outcome. Safety is a different endpoint entirely and would require separate data on adverse events.

Note: ⚠️ Note the internal inconsistency in the source item: a point estimate of 3.1 cannot lie outside its own confidence interval of 3.4–4.7. The examinable logic is unaffected — CI excludes 1 and p < 0.05, therefore significant — but the numbers as recalled are impossible. Useful teaching point in itself.