Standard Deviation Error Bars for Individual Columns of a Bar Chart

Hi everyone!

I am writing my thesis and I am having some troubles with adding standard deviation bars to my chart. I have a series of average times per task. So I had 2 independent groups test an interface twice. I took their average time for each task for one group and the other group. So I get a table like this:

	A	B	A	B
	3D USER	3D USER	2D USER	2D USER
Average Time Taken for Task 1	552.89	356.23	494.44	178.98
Average Time Taken for Task 2	147.78	65.75	170.26	85.09
Average Time Taken for Task 3	396.56	255.26	395.68	186.04
Average Time Taken for Task 4	232.16	161.25	173.43	200.27

This way I can create a 2D bar chart that looks like this:

Chart.png

As you can see the error bar is the same for all blue bars. Each blue bar is a different time for a totally different task. How do I add a an error bar, I can use my own custom value for standard deviation I have calculated earlier, but I cant get it to be separate for each bar.

Hope I was clear enough.

Here is an explanation of how to use custom error bar values.
http://peltiertech.com/WordPress/cus...-excel-charts/