# Can I use Standard deviation (in Excel error bars) with median in a graph?

I have a variable (vitamin D levels) that does not follow normal distribution. I wanted to plot its variation throughout a period of time. I used the median. However I wanted to add error bars in this Excel graph. I used standard deviation but I don't know if it is correct. If it is not, what other measure of dispersion should be used?

• Correct or not, that would certainly be unconventional and is likely to be puzzling or surprising to many readers and might be challenged by anyone in authority (peers, examiners, reviewers). Show median and quartiles usually. But there is no reason why apparent lack of normality need stop you looking at the mean too. The mean is a standard parameter for several non-normal distributions e.g. the exponential. What stops you showing mean and median too? Commented Dec 14, 2016 at 19:37
• stats.stackexchange.com/questions/190223/… shows one among many possibilities. No rule I would want to respect prohibits showing mean and median too if that is helpful. Commented Dec 14, 2016 at 19:40
• How to do anything in Excel is off-topic here and in any case I am not a person to advise. Commented Dec 14, 2016 at 19:41
• If the variables are iid and continuous with a known density the distribution of the sample median can be obtained. Look at Wikipedia's topic "order statistics". If you can make all these assumptions except for known density you can use the bootstrap. Commented Dec 14, 2016 at 19:53
• Perhaps you can use Median Absolute Deviations (MAD) for your median column as error bars. Both are non-parametric, and perhaps the best bet. Commented Aug 28, 2018 at 8:36