Updated: 9 August 2010
Use CONFIDENCE to calculate a value that you can use to construct a confidence interval for a population mean. Confidence intervals are used to indicate the reliability of an estimate.
Syntax
SELECT [wctStatistics].[wct].[CONFIDENCE] (
<@Alpha, float,>
,<@Standard_dev, float,>
,<@Size, float,>)
Arguments
@Alpha
is the significance level use to compute the confidence interval. The confidence interval equals 1-@Alpha. @Alpha is an expression of type float or of a type that can be implicitly converted to float.
@Standard_dev
is the population standard deviation for the dataset. @Standard_dev is an expression of type float or of a type that can be implicitly converted to float.
@Size
is the sample size. @Size is an expression of type float or of a type that can be implicitly converted to float.
Return Types
float
Remarks
· If @Alpha ≤ 0 or @Alpha≥ 1, CONFIDENCE returns an error.
· If @Standard_dev ≤ 0, CONFIDENCE returns an error
· @Size is truncated to zero decimal places.
· If @Size < 1, CONFIDENCE returns an error
· CONFIDENCE = NORMSINV(1-@Alpha/2)*(@Standard_dev/SQRT(@Size))
Examples
select wct.CONFIDENCE(.025,6.25,150)
This produces the following result
----------------------
1.14381103915062
(1 row(s) affected)
select wct.NORMSINV(.9875)*(6.25/SQRT(150))
This produces the following result
----------------------
1.14381103915062
(1 row(s) affected)