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XLeratorDB/statistics Documentation

SQL Server standard deviation function


 
Updated: 6 August 2010
Use STDEV_q to return the estimated standard deviation based on a sample. The standard deviation is a measure of how widely values are dispersed from the mean. The equation for STDEV_q is:
 
 STDEV
Syntax
SELECT [wctStatistics].[wct].[STDEV_q] (
   <@Values_RangeQuery, nvarchar(4000),>)
Arguments
@Values_RangeQuery
the select statement, as text, used to determine the values to be used in the STDEV_q calculation.
Return Types
float
Remarks
·         If you want measure the standard deviation for an entire population, then use the STDEVP_q function.
·         For simpler queries or for queries on de-normalized data, use the STDEV 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.STDEV_q('SELECT num from #k1')
 

This produces the following result

----------------------
11.0303511188038
 
(1 row(s) affected)


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