How to Graph Error Bars in Illustrator
Illustrator's Column graph tool doesn't have a feature for drawing error bars, but you can use the Line Segment tool to create this graphic. Note that the error bars you create with Line Segment aren't part of the Column graph object. This means that when you move either the graph or the error bar, the other remains in place. To avoid this problem, use the Object menu's Group command to link all error bars with the graph.
Click the "File" menu's "New" command, then click "OK" to accept the default parameters for a new canvas. Illustrator creates the canvas.
Click the "Tools" panel icon shaped like a bar chart to run the Column graph tool, then click on the canvas where you want the graph's top left corner to appear. Drag down and right until the graph reaches the size you want, then click the mouse to complete the graph.
Type the data for the graph into the gridded dialog box that appears. You can type "1," then "2" for sample data to create two different columns for the graph.
Click the check mark icon on the dialog's toolbar to plot the sample data.
Click the "Tools" panel icon shaped like a straight line segment to run the Line Segment tool, then press and hold "Shift" to indicate you want to draw a straight line.
Click the mouse directly above the first column of your graph, at the "Y" coordinate at which you'd like to line's top to appear. For example, if you want the error bar to extend from the "1.5" mark down to the "0.75" mark, position your mouse so it's aligned horizontally with the "1.5" mark of the "Y" axis, then click the mouse to plot the leftmost error bar's top point.
Drag directly downward until your mouse is aligned with the "Y" axis point that matches the lower number of your error range for the current column. Click the mouse to complete the line segment representing the error bar.
Create the error bar for the remaining columns in your graph as you did the first column to complete the graph with its error bars.