# SQL Sequence Grand Aggregate Var and Dev Functions

> The `seq_var()` and `seq_dev()` functions compute the variance and standard deviation for the input sequence, and return a double value. The variance is always a positive number; the smaller the value the closer the values of the sequence elements are to the mean. The standard deviation returned by `seq_dev()` is the square root of the variance.

> Following is an example script demonstrating the `seq_var()` and `seq_dev()` functions:

>         INSERT INTO SimpleSequence(testNumber,fVal1)
>         VALUES(4,'{2,3,5,7}');

>         SELECT fVal1, seq_var(fVal1) AS "var", seq_dev(fVal1) AS "dev"
>         FROM SimpleSequence WHERE testNumber = 4;

>         fVal1{}
>         var
>         dev
>         ------------------------------------------------------------------------
>         {2.000000, 3.000000, 5.000000, 7.000000}
>         3.687500
>         1.920286

> The variance and standard deviation calculation for Grand_Agg, Group_Agg, Grid_Agg and Window_Agg functions implement the “population variance” method and can be verified using the excel `VAR.P()` and `STDEV.P()` functions (see http://www.excelfunctions.net/variance-in-excel.html for an explanation of these two statistical analysis methods).

> ## Sample script

> A sample script to demonstrate this `select` statement using xSQL can be run from the `samples/xsql/scripts/financial` directory with the following command:

>         f 1