How variable numbers are from the average. The smaller the standard deviation, the tighter the spread. For example, on average 10 oocytes are retrieved. If 100 people get between 8-12 this is low deviation, vs 100 people getting between 0-20 (high deviation).
Sometimes standard deviation is used to show the variability in a number (followed by a ยฑ). A single standard deviation represents 68% of the data, and 3 standard deviations are needed to show all the data. You can read more about that here (no paywall for this post).
Synonyms:
SD