Excluding complications like difficulty changes and temporary blockchain splits, you can model the block generation time as an exponential distribution.
An exponential distribution has a standard deviation equal to the expectancy value. This predicts a 10 minute standard deviation for Bitcoin.
Measuring the actual distribution isn't that easy. While each block contains a timestamp, that timestamp isn't very accurate, and sometimes the time difference between blocks is even negative.
The timestamp doesn't change over the course of a single share, and some miners deliberately use timestamps deviating from the actual time