Because when we use the average to represent the "centralized trend" of a data, if one or two extreme data appear in the data, the representative function of the average for this group of data will be weakened. In order to eliminate this phenomenon, we can remove several extreme data, only calculate the average value of the remaining data, and take the obtained result as the average value of all data.

Mathematical calculation method:

Arithmetic average is influenced by extreme value;

In many cases, we need to eliminate the influence of extreme value on average value. For example, in literary or sports competitions, we need to remove several highest scores and several lowest scores, and then calculate the average of the remaining data, which is the truncated average.