How to use TRIMMEAN Function in Excel

The TRIMMEAN function 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)

The TRIMMEAN function syntax has the following arguments:

• Array    Required. The array or range of values to trim and average.

• Percent    Required. 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.

Example: Let’s look at some Excel TRIMMEAN function examples and explore how to use the TRIMMEAN function as a worksheet function in Microsoft Excel:

Syntax:  =TRIMMEAN(B2:B17,0.1)

Result: 64125

Based on the Excel spreadsheet above, the following TRIMMEAN examples would return:

Note:

• 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.
• If percent < 0 or percent > 1, TRIMMEAN returns the #NUM! error value.
• If the supplied array is empty, TRIMMEAN returns the #NUM! error value.
• If the percent is non-numeric, TRIMMEAN returns the #VALUE! error value.