Confirmatory research normally involves formal testing of one or more prespecified hypotheses. By contrast, exploratory research normally involves looking for patterns in the data with less emphasis on formal testing of hypotheses. Commonly, exploratory experiments involve many characters. For example, many microarray experiments in which up or down regulation of many thousands of genes is assayed in each animal could be classified as exploratory experiments because the main purpose is usually to look for patterns of response rather than to test some prespecified hypotheses. There is frequently some overlap between these two types of experiment. For example, an experiment may be set up to test whether a compound produces a specific effect on the body weight of rats—a confirmatory study. However, data may also be collected on hematology and clinical biochemistry, and exploratory investigations using these data may suggest additional hypotheses to be tested in future confirmatory experiments.