Which statement describes what a confidence interval that does not cross 1 for a risk estimate indicates at alpha 0.05?

• A. Imprecise estimate
• B. Statistically significant
• C. Not significant
• D. Large sample size

Answer: (B)

When interpreting a confidence interval around a risk ratio (or odds ratio), 1 represents no difference in risk. If the entire interval lies above 1 or entirely below 1, the null value of no effect is not plausible at the chosen confidence level. At alpha 0.05, that means the result is statistically significant. In other words, the observed association is unlikely to be due to chance. The width of the interval reflects precision, not significance itself—so a not-crossing-1 interval can be wide or narrow, but it still indicates a significant effect. Conversely, if the interval includes 1, the result is not statistically significant.