Pseudo Standard Deviation
If the data has a normal distribution, the standard deviation would be equivalent to (quantile(75%)-quantile(25%))/1.349
The Pseudo Standard-Deviation is more robust then the regular Standard Deviation, i.e. less vulnerable to outliers.
OBS. I hope this is only on my page now, and not public. If so, I'm sorry about that. I still have more to include here, as the references.