Answer:
The mean.
Explanation:
The mean is not robust.
The presence of an outlier greatly affects the value of a mean.
An example will illustrate this.
Find the mean of the numbers 2 3 5 6 34.
34 is an outlier. The mean = (2+3+5+6+34) / 5 = 10.
Now if we replace the outlier with a number closer to the others:
Say we have 2 3 5 6 8 :
The mean = (2+3+5+6+8) / 5 = 4.8 which is a much truer measure of centrality than 10.