In systematic reviews homogeneity refers to the degree to which the results of studies included in a review are similar. Clinical homogeneity means that, in trials included in a review, the participants, interventions and outcome measures are similar or comparable. Studies are considered statistically homogeneous if their results vary no more than might be expected by the play of chance, though most statistical tests would say that 10% of a perfectly homogeneous data set was heterogeneous, because that is the usual set-point for the tests.