Updated: 6 August 2010
Use VAR_q to estimate variance based on a sample. To estimate the population variance from a sample of N elements with an unknown mean (the mean being calculated from the sample itself):
Syntax
SELECT [wctStatistics].[wct].[VAR_q] (
<@Values_RangeQuery, nvarchar(4000),>)
Arguments
@Values_RangeQuery
the select statement, as text, used to determine the values used in the VAR_q function.
Return Types
float
Remarks
· If you want measure the population variance, then use the VARP_q function.
· For simpler queries or for queries on de-normalized data, use the VAR function.
· No GROUP BY is required for this function even though it produces aggregated results.
Examples
CREATE TABLE #k1(
[num] [float] NOT NULL
)
INSERT INTO #k1 VALUES (91.3698)
INSERT INTO #k1 VALUES (76.3382)
INSERT INTO #k1 VALUES (74.5692)
INSERT INTO #k1 VALUES (85.2957)
INSERT INTO #k1 VALUES (99.0112)
INSERT INTO #k1 VALUES (86.99)
INSERT INTO #k1 VALUES (70.7837)
INSERT INTO #k1 VALUES (72.834)
INSERT INTO #k1 VALUES (78.1644)
INSERT INTO #k1 VALUES (77.7472)
INSERT INTO #k1 VALUES (66.0627)
INSERT INTO #k1 VALUES (59.781)
INSERT INTO #k1 VALUES (68.4793)
INSERT INTO #k1 VALUES (78.6103)
INSERT INTO #k1 VALUES (59.8621)
select wct.VAR_q('SELECT num from #k1')
This produces the following result
----------------------
121.668645804095
(1 row(s) affected)