Visual illusions created by survival curves and the need to avoid potential misinterpretation.

Randomized clinical trials play an increasingly important role in guiding management decisions, and survival curves are the most popular means for summarizing and depicting the results of a clinical trial. However, survival curves may create certain "visual illusions" that can be misinterpreted by the unwary, with potentially adverse effects on patient care. The authors provide a brief outline of the theoretical background of survival curves and explain the origin of the most common visual illusions. Statisticians need to be aware of such potential for misinterpretation of clinical trial data in order to safeguard clinicians against drawing undue inferences and applying them to actual practice.