The grand mean is the mean of all the means coming from different sub-samples.
Find out the grand mean for the following two sets named as, A&B. A = (2,3,4); B = (6,7,1,9)
Set A = 2,3,4
Set B = 6,7,1,9
Substitute the given values into the formula to solve grand mean, = Sum of the Mean of all Sets / Total Number Sets = [ (2+3+4) / 3 ] + [ (6+7+1+9) / 4 ] / 2 = ( 3 + 5.75 ) / 2 = 4.375