Question

How do you calculate the average difference of 2 means that do not have the same number of values

Answer 1

can you give an example?

Answer 2

do an example
let
X = { 1, 2, 3, 4, 5, }
Y = { 4 , 5, 6, 7}

X - Y = { (1-4) , (2-4), (3-4), (4-4), (5-4), ... (5-7) }
X and Y don't have same number of elements

mean X = 3
mean Y = 5.5