TRIMMEAN

See Also

Returns the mean of the interior of a data set. TRIMMEAN calculates the mean taken by excluding a percentage of data points from the top and bottom tails of a data set. You can use this function when you wish to exclude outlying data from your analysis.

Syntax

TRIMMEAN(array,percent)

Array is the array or range of values to trim and average.

Percent is the fractional number of data points to exclude from the calculation. For example, if percent = 0.2, 4 points are trimmed from a data set of 20 points (20 x 0.2): 2 from the top and 2 from the bottom of the set.

Remarks

If percent < 0 or percent > 1, TRIMMEAN returns the #NUM! error value.
TRIMMEAN rounds the number of excluded data points down to the nearest multiple of 2. If percent = 0.1, 10 percent of 30 data points equals 3 points. For symmetry, TRIMMEAN excludes a single value from the top and bottom of the data set.

Example

The example may be easier to understand if you copy it to a blank worksheet.

Show How?

Create a blank workbook or worksheet.
Select the example in the Help topic. 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 Tools menu, point to Formula Auditing, and then click Formula Auditing Mode.

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Formula	Description (Result)
=TRIMMEAN(A2:A12,0.2)	Mean of the interior of a data set above, with 20 percent excluded from calculation (3.777778)