The Excel STDEVA Function

Related Function:
STDEV Function
Standard Deviation

The Standard Deviation is a statistical measure, that is closely linked to the Variance. Both measures are commonly used across a set of values, to identify the amount that the values differ (or deviate) from the average value.

When your data set is a sample of a population, (rather than an entire population), you should use a slightly modified form of the Standard Deviation, known as the Sample Standard Deviation. The equation for this is:

Sample Standard Deviation Equation

where,

  • x takes on each value in the set;
  • x is the average (statistical mean) of the set of values;
  • n is the number of values.
Further information is provided on the Wikipedia Standard Deviation page

Basic Description

The Excel STDEV function calculates the sample standard deviation of a supplied set of values.

The syntax of the function is:

STDEV( number1, [number2], ... )

where the number arguments are one or more numerical values, arrays of values, or references to cells containing numbers.

If you are using a recent version of Excel (2007 or later), you can enter up to 255 number arguments to the function. However, in Excel 2003, the function can only accept up to 30 number arguments.

Note that the Stdev function is used when calculating the standard deviation for a sample of a population (e.g. if your data set records the individual heights of a sample of UK males). If you are calculating the standard deviation of an entire population, you should use the Stdevp or the Stdevpa function.


STDEVA & STDEV Functions

The Excel Stdeva function is very similar to the Excel Stdev function, in that both functions calculate the sample standard deviation of a supplied set of values.

The difference between these two functions applies when an array of values, containing text or logical values is supplied to the function. In this case, the Stdev function ignores the text and logical values, whereas the Stdeva function assigns the value 0 to text and the values 1 or 0 to logical values.

The rules for this are shown in the table below, compared to the rules for the Stdev function.

STDEV FunctionSTDEVA Function
Logical values or text (including text representations of numbers), typed directly into the list of argumentsARE counted
(TRUE=1, FALSE=0)
ARE counted
(TRUE=1, FALSE=0)
Text that cannot be interpreted as a number, typed directly into the list of arguments#VALUE! error#VALUE! error
Logical values, within arrays or reference argumentsIgnoredARE counted
(TRUE=1, FALSE=0)
Text (including empty text "", text representations of numbers, or other text), within arrays or reference argumentsIgnoredCounted as zero
Empty cellsIgnoredIgnored

See the page on Standard Deviation in Excel for a comparison of all the different Excel standard deviation functions.

Stdeva Function Example

The following spreadsheet shows the Excel Stdeva function used to calculate the standard deviation of the set of values in cells A1-A4 and in cells A1-A6.

 Formulas:
 AB
11=STDEVA( A1:A4 )
23=STDEVA( A1:A6 )
35=STDEVA( A1:A4, 1, 0 )
42 
5TRUE 
6text 
 Results:
 AB
111.707825128
231.788854382
351.788854382
42 
5TRUE 
6text 

Note that, in the spreadsheet above, the function in cell B2 includes the values in cells A5 and A6. In this case, the logical value TRUE in cell A5 is treated as the value 1 and the text in cell A6 is treated as the value 0. This is shown by the example in cell B3, in which cells A1-A4 and the values 1 and 0 give the same result as the standard deviation calculation for cells A1-A6.


Further information and examples of the Excel Stdeva function are provided on the Microsoft Office website.


Stdeva Function Errors

If you get an error from the Excel Stdeva function this is likely to be one of the following:

Common Errors
#DIV/0!-Occurs if fewer than two numeric values are supplied to the Stdeva function.
#VALUE!-Occurs if any values that are supplied directly to the Stdeva function are text values that cannot be interpreted as numeric values.