To add a reference line, select a chart item that represents a data fact and on the shortcut menu, select Add Reference Line.
To modify a reference line:
Double-click the reference line.
The Reference Properties dialog box is displayed.
Select Fixed to assign an axis based reference line, or a fact item from the Fact drop-down.
For more information about adding fixed and fact based reference lines, see Reference Line Properties.
To assign a statistical function to a fact based reference line, select a function from the Function drop-down list.
Select the Line Style tab, and select any line style properties.
For more information, see Reference Line Style Properties.
Select the Label Format tab, any select any label properties.
For more information, see Reference Line Label Format Properties.