Returns the mean of a set of numbers, ignoring a proportion of high and low values.


TRIMMEAN(numberlist, fraction)

numberlist is a range or array of numbers, not necessarily in order. TRIMMEAN returns the mean, ignoring a fraction (0 <= fraction < 1) of the outermost values in numberlist.
Specifically, where n is the count of numbers in numberlist, the highest and lowest INT(n * fraction / 2) values are ignored.


TRIMMEAN(A1:A100, 0.1)
returns the mean of the values in cells A1:A100, ignoring the lowest 5 values and the highest 5 values.

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