In the following figure the error bars represent the standard error of the mean and the difference between groups has not been examined.

21 20 19 18 17 16 15 14 13 12 11 10 Control (n = 36) Exp (n = 25)( x -X2 ) - ( 14 - Hz 1 2 2 (n, - 1)s, + (n2 - 1)s2 S. S 1 + 2 ntn 2 - 2 n n2