USMLE purpose: Interpret relative risk and confidence intervals, especially whether a result is significant and what percent risk reduction means.

How to use this page

  1. Start by checking whether the confidence interval crosses 1.
  2. For RR below 1, convert the reduction as 1 − RR.
  3. For RR above 1, interpret increased risk.
  4. Use the answer toggles to test yourself before reading explanations.

One-liner

For relative risk, 1 means no difference; if the confidence interval includes 1, the result is not statistically significant.

Interpretation table

Result Meaning Exam conclusion
RR = 1 No difference Exposure does not change risk
RR < 1 Risk is lower Protective / risk reduction
RR > 1 Risk is higher Risk increase
CI includes 1 Could be no difference Not statistically significant
CI entirely below or above 1 Does not include no-effect value Statistically significant

Worked example

RR = 0.70 with 95% CI 0.60–0.92.

Board Exam Buzzwords

Phrase What it means Answer style
RR 0.70 30% lower risk Reduced risk
CI 0.65–1.15 Includes 1 No significant difference
Two treatments similar at endpoint No superiority Neither drug superior

Anki-style rapid recall