Aggregate. Computes the standard deviation of a population consisting of a numeric-expression, as a float.
Syntax
stddev_pop ( numeric-expression )
Parameters
| numeric-expression | The expression, usually a column name, for which the population-based standard deviation is calculated over a set of rows. |
Usage
This function converts its argument to float, performs the computation in double-precision floating point, and returns a float. The standard deviation is used to find the amount of variation between data points and the groups average. The population-based standard deviation is computed according to the following formula:
This standard deviation does not include rows where numeric-expression is NULL. The function returns NULL for a group containing no rows.
The standard deviation of a population could be used to estimate and assess changes in securities, which could be used to establish future expectations.