Standard Error Bars.

[A S-D]

I've an error bar query.

I've calculated the standard error margin (SEM) for each point in my bar graph - this varies as each point is the average of a varying number of samples.

This SEM value is represented in the same units as the data on the bar graph (second), and is in a column that corresponds to the values for the bars in the bar graph. (i.e. A1 = Bar 1 value, B1 = Bar 1 value SEM).

When I define the error bar using the 'custom error bars' option in the 'add error bars' tab I select the column (I drag from the top of the SEM data to the bottom) for the SEM data. However, Excel gives seemingly spurious error bars when I do this. I'm getting errors of several times the values according to the error bars, when the actual SEM is equal to zero, for example.

How do I define the error bars correctly? Is because I am working in seconds?

I have attached the sheet. The values of the bar chart are in column AU, and the values of each point's SEM is in column BB.

(You'll also notice the ridiculous formula I came up with for calculating the SEM! I'm not very good with Excel!)

Thanks for your help,

Adam

[A S-D]

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