Returns the mean of a data set without the Alpha percent of data at the margins.
Data is the array of data in the sample.
Alpha is the percentage of the marginal data that will not be taken into consideration.
=TRIMMEAN(A1:A50; 0.1) calculates the mean value of numbers in A1:A50, without taking into consideration the 5 percent of the values representing the highest values and the 5 percent of the values representing the lowest ones. The percentage numbers refer to the amount of the untrimmed mean value, not to the number of summands.