grand mean
a numerical average (mean) of a group of averages. For example, if the average test score for one classroom is 75 and the average score for another classroom is 73, the grand mean of the two classrooms is (75 + 73)/2 = 74. Similarly, if an analysis of variance reveals average values of 3, 10, and 20 on a response or dependent variable for three groups of study participants, the grand mean of scores—that is, the average of all participants’ responses regardless of the condition of the independent variables—is (3 + 10 + 20)/3 = 11.