A strategy to use soft data effectively in randomized controlled clinical trials.

Soft data are defined as measures having substantial intrasubject variability due to errors of measurement or to the inconsistency of subjects' responses. Such data are often important measures of response in randomized clinical trials. In this context, we show that using an intensive design and the slope of response on time as the outcome measure (a) maximizes sample retention and (b) decreases within-group variability, thus (c) maximizing the power of test procedures without requiring increased sample sizes.