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Average Deviation

The Average Deviation, like the Standard Deviation, measures the deviation of a set of points from their average.

The Average Deviation is calculated by the following equation:

where x takes on each value in the set, x is the average (statistical mean of the set of values, and n is the number of values.

The Excel AVEDEV function calculates the average deviation of a supplied set of values.

The format of the function is:

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

where the arguments, number1, [number2], etc, are one or more numeric values (or arrays of numeric values) that you want to find the average deviation of.

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

Note that the Avedev function ignores logical values and text values (including text representations of numbers) if these are supplied as part of an array. However, the function __does__ count text representations of numbers and logical values that are supplied directly to the function as individual number arguments.

A company keeps a record of its monthly sales figures, over three years. These are stored in cells B3 - B14, D3 - D14 and F3 - F14 of the above spreadsheet on the right.

The average deviation of the three years' sales figures is calculated in cell H3 of the spreadsheet. The formula for this, as shown in the formula bar, is:

=AVEDEV( B3:B14, D3:D14, F3:F14 )

As shown in cell H3, the average deviation for the 3 years of sales figures is calculated to be **2,027.78**.

In the example above, the arguments to the Avedev function are input as 3 cell ranges. However, you can also input figures directly, as individual numbers or number arrays.

For example, if, during January and February 2010 the sales figures are 13,000 and 14,500, you could add these directly into the above function as follows:

Either as individual numbers:

Or, as an array of numbers:

This gives the updated average deviation value of **1,973.68**.

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

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

Common Errors

#DIV/0! | - | Occurs if none of the values supplied to the function are numeric. (Note that text representations of numbers, that are supplied as a part of an array, are not interpreted as numeric values by the Avedev function). |

#VALUE! | - | Occurs if any of the number arguments that are supplied directly to the Avedev function are non-numeric text strings. |