When is a negative study not negative?

Results of Phase III randomized clinical trials can be categorized into three groups: positive, null, and negative. The jargon used in discussing results of comparative studies requires clarification because misclassification can result in incorrect interpretation. A positive result indicates that the experimental therapy(ies) is(are) superior to standard therapy. A null result indicates that no statistically significant difference between therapies was found; hence, standard therapy should not be replaced. A negative result indicates that the experimental therapy had a deleterious effect compared to standard therapy. This article presents a discussion of these categories and examples of each.