CONFIDENCE(alpha, standard_dev, size)

Returns the confidence interval for a population mean.

alphaThe significance level used.
standard_devThe population standard deviation for the data range.
sizeThe size of the sample.

Remarks

* CONFIDENCE.NORM was added in Excel 2010 to replace this function.
* The confidence level equals 100*(1 - alpha)%.
* An alpha of 0.05 indicates a 95 percent confidence level.
* An alpha of 0.1 indicates a 90 percent confidence level.
* If any of the arguments are not numeric, then #VALUE! is returned.
* If "alpha" = 0, then #NUM! is returned.
* If "alpha" = 1, then #NUM! is returned.
* If "standard_dev" = 0, then #NUM! is returned.
* If "size" is not an integer, it is truncated.
* If "size" < 1, then #NUM! is returned.
* For the Microsoft documentation refer to support.office.com

 A
1=CONFIDENCE(0.05,2.5,50) = 0.693
2=CONFIDENCE(0.05,2.5,50.25) = 0.693
3=CONFIDENCE(-1,2.5,50) = #NUM!
4=CONFIDENCE(0.05,0,50) = #NUM!
5=CONFIDENCE(1,2.5,50) = #NUM!
6=CONFIDENCE("some text",2.5,50) = #VALUE!


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