Using an Excel graph (chart), I am trying to show three things: 1) the number of voters in each of 25 wards in a Mid-western city; 2) the average of these 25 numbers; and 3) the standard deviation. I've got a line graph showing the number of voters, low to high, with the ward identifiers as the X-axis, but I can't seem to draw a straight horizontal line showing the average, and I haven't even tried to show the S.D. yet. Any suggestions? Thanks.