AJP Excel Information

Re: Show mean as a vertical line in a graph?

Create a stacked bar chart and then move the Mean and Line series to the secondary axis.
Change the chart type for the Mean series to Stacked Bar.
Format the Mean series to have no fill or border and set the Gap Width to zero.
Delete the Secondary X and Y axis 

As suggested by Bill Dilworth

Create a clustered bar chart.
Add a linear trendline to the Mean series.
Format the Mean series to have no fill or border and set the Overlap to 100.

Example file