This article describes the formula syntax and usage of the STDEVA function in Microsoft Excel.
Description
Estimates standard deviation based on a sample. The standard deviation is a measure of how widely values are dispersed from the average value (the mean).
Syntax
STDEVA(value1, [value2], ...)
The STDEVA function syntax has the following arguments:

Value1, value2, ... Value1 is required, subsequent values are optional. 1 to 255 values corresponding to a sample of a population. You can also use a single array or a reference to an array instead of arguments separated by commas.
Remarks

STDEVA assumes that its arguments are a sample of the population. If your data represents the entire population, you must compute the standard deviation using STDEVPA.

The standard deviation is calculated using the "n1" method.

Arguments can be the following: numbers; names, arrays, or references that contain numbers; text representations of numbers; or logical values, such as TRUE and FALSE, in a reference.

Arguments that contain TRUE evaluate as 1; arguments that contain text or FALSE evaluate as 0 (zero).

If an argument is an array or reference, only values in that array or reference are used. Empty cells and text values in the array or reference are ignored.

Arguments that are error values or text that cannot be translated into numbers cause errors.

If you do not want to include logical values and text representations of numbers in a reference as part of the calculation, use the STDEV function.

STDEVA uses the following formula:
where x is the sample mean AVERAGE(value1,value2,…) and n is the sample size.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Data 

Strength 

1345 

1301 

1368 

1322 

1310 

1370 

1318 

1350 

1303 

1299 

Formula 
Description (Result) 
Result 
=STDEVA(A3:A12) 
Standard deviation of breaking strength for all the tools (27.46391572) 
27.46391572 