TRIMMEAN

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

TRIMMEAN({4,5,6,7,2,3,4,5,1,2,3},0.2) equals 3.777778