In a positive trial, why should researchers examine the lower limit of a confidence interval?

Examining the lower limit of a confidence interval in a positive trial is essential because it provides critical information about the smallest effect size that can be reasonably expected. The minimal clinically important difference (MCID) refers to the smallest change in a treatment outcome that is considered significant enough to impact patient care. By assessing whether this lower limit is above the MCID, researchers can determine if the observed effect of the intervention is not only statistically significant but also clinically meaningful. This step is crucial in translating research findings into practical applications in clinical settings, ensuring that the intervention has real-world value for patients.

In assessing treatment effects, simply looking at the point estimate of the effect size does not give a full picture, as it lacks the nuance that the confidence interval provides. While other options might be relevant in different contexts, they do not directly address the specific importance of the lower limit in terms of clinical significance.