If a study reports p<0.001 for an association, what does this imply?

• A. The result is not statistically significant
• B. The result is statistically significant
• C. The sample size is small
• D. The confidence interval includes 1

Answer: (B)

A p-value below 0.001 shows very strong evidence against no association. It means that if there really were no association, the probability of observing an association as extreme as what was found (or more extreme) is less than 0.1%. Because this probability is so small, the result is considered statistically significant and would typically lead researchers to reject the null hypothesis.

Keep in mind that statistical significance isn’t the same as practical importance. A very small p-value can occur with a large sample even if the actual effect is tiny, while a meaningful real-world impact might still be modest in size. Relatedly, such a small p-value usually aligns with a confidence interval that does not include the null value (for example, a relative risk or odds ratio not crossing 1), reinforcing the idea that the effect is unlikely to be due to random chance.