so mean also translates to average so
the mean of 4 numbers is aprox
x=average
(x+x+x+x)/4=average
to increase x by 2 you add 2
x+2=average
(x+2+x+2+x+2+x+2)=4=(4x+8)/4=x+2
you would have to increase the sum/total by 8 to make the numbers' averages' go up by 2
