Design and analysis of controlled clinical trials in rheumatic diseases.

Controlled clinical trials can be difficult, expensive, and time-consuming, but are necessary to advance the knowledge concerning rheumatic disease. Proper care in the design of the study and appropriate statistical analysis of the data can result in studies that answer specific questions and are well worth the effort and expense. If the design is well planned before the entry of the first patient, many problems will be avoided and the results will be credible.