The Excel SKEW Function

Related Function:
KURT Function

Skewness
The Skew of a data set is a measurement of the asymmetry of the distribution about the mean.
  • A skew of zero indicates perfect symmetry
  • A positive skew indicates that more values lie below the mean and the distribution has a 'tail' which extends towards the higher values
  • A negative skew indicates that more values lie above the mean and the distribution has a 'tail' which extends towards the lower values
Examples of positive and negative skewed distributions are shown in the charts below:
Examples of Positive and Negative Skewed Distributions
Positive Skew Negative Skew

For more information on skewness, see the Wikipedia page



Basic Description

The Excel SKEW function calculates the skewness of the distribution of a supplied set of values.

The format of the function is :

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

Where the number arguments provide a minimum of 3 values that make up the data set. These can be individual numbers or arrays of numbers and can be input either directly, as returned values from other functions or formulas, or as references to cells containing values.

In Excel 2007, you can input up to 255 number arguments to the Skew function, but in Excel 2003, you can only input up to 30 arguments.


  A B
1 1  
2 1  
3 2  
4 2  
5 2  
6 2  
7 3  
8 3  
9 3  
10 4  
11 4  
12 5  
13 6  
14 7  
15 8  

Skew Function Example

Column A of the spreadsheet on the right shows 15 data values. The distribution of these values is shown in the chart below:

Distribution of Points in Skew Function Example

The skewness of the values in the spreadsheet can be calculated using the Excel Skew Function as follows:

=SKEW( A1:A15 )

This gives the result 0.863378312, indicating that the data set has a positive skew.


Further information and examples of the Excel Skew function can be found on the Microsoft Office website.


Skew Function Error

If you get an error from your Excel Skew function this is likely to be the Excel #DIV/0! error:

Common Error
#DIV/0! - Occurs if either:
- Fewer than 3 data values have been supplied to the function
or
- The sample standard deviation of the data points is zero
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