CDISC-Gloss – The assertion that no true association or difference in the study outcome or comparison of interest between comparison groups exists in the larger population from which the study samples are obtained. NOTE: A null hypothesis (for example, “subjects will experience no change in blood pressure as a result of administration of the test product”) is used to rule out every possibility except the one the researcher is trying to prove, and is used because most statistical methods are less able to prove something true than to provide strong evidence that it is false. The assertion that no true association or difference in the study outcome or comparison of interest between comparison groups exists in the larger population from which the study samples are obtained. See also research hypothesis. [from AMA Manual of Style]