(plural standard deviations)
Coined by English mathematician Karl Pearson in 1894 in his paper "On the dissection of asymmetrical frequency curves".
standard deviation - Computer Definition
In statistics, the average amount a number varies from the average number in a series of numbers.
standard deviation - Investment & Finance Definition
The degree that a single value in a group of values varies from the mean (average) of the distribution. Standard deviation is a statistical measure that uses past performance of an investment or portfolio to determine the potential range of future performance and assess the probability of that performance. Standard deviations can be calculated for an individual security or for the entire portfolio.