You can move the 2 blue points on the x-axis to show the probability in the left and right tails and the center. When you check [b]Equal Tails[/b], the tails become symmetric and the total probability in the tails [math]\alpha[/math] is shown. You can then also give a numeric value for [math]\alpha[/math] and the tails will be adjusted. Select[b] [color=#1155cc]Cumulative[/color][/b] [b][color=#1155cc]Normal[/color][/b] to view an overlay of the cumulative distribution along with the tails.