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
STDEV(number1,number2,...)
Number1, number2, ... are 1 to 30 number arguments 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
 STDEV assumes that its arguments are a sample of the population. If your data represents the entire population, then compute the standard deviation using STDEVP.
 The standard deviation is calculated using the "n1" method.
 Arguments can either be numbers or names, arrays, or references that contain numbers.
 Logical values and text representations of numbers that you type directly into the list of arguments are counted.
 If an argument is an array or reference, only numbers in that array or reference are counted. Empty cells, logical values, text, or error 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 want to include logical values and text representations of numbers in a reference as part of the calculation, use the STDEVA function.
 STDEV uses the following formula:
where x is the sample mean AVERAGE(number1,number2,…) and n is the sample size.
Example
Suppose 10 tools stamped from the same machine during a production run are collected as a random sample and measured for breaking strength.
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

A 
Strength 
1345 
1301 
1368 
1322 
1310 
1370 
1318 
1350 
1303 
1299 
Formula 
Description (Result) 
=STDEV(A2:A11) 
Standard deviation of breaking strength (27.46391572) 
