@helmut_meukel
mean is the same as the median.
No, it is a little more complicated, at least statistically.
Here is something I found on-line that may help. At least I don't have to confuse you with another measure of central tendency, the mode. (The most common number in the progression.)
"Are mean and median the same thing?
4 Answers
Anirvan Maiti
Anirvan Maiti, M.S. from Boston University
Updated Aug 16 2015
Lets say we have a set of 7 numbers as follows :
72, 2, 6, 32, 55, 15, 9
Mean
Mean is the average of a set of numbers.
So the mean for the above given set of numbers is :
72+2+6+32+55+15+9
7
Which gives the answer : 27.2857
Median
Median is the middle element in an ordered set.
So, if we arrange the above set in an ascending order, we get :
2, 6, 9, 15, 32, 55, 72
We see that the middle most element in this ordered set is the number 15
Therefore, 15 is the median of the set.
Difference between Mean and Median (CONCEPT)
In the above given set of ordered numbers, if I change the last number 72 to 99999, the mean becomes
2+6+9+15+32+55+99999
7
which is equal to 14302.5714
BUT
The median of this set still remains the same. Because in this set
2, 6, 9, 15, 32, 55, 99999
the middle element still remains the same, which is 15
Relation between Mean and Median
If we have a set where every number is equidistant from its predecessor (or successor) like
3, 6, 9, 12, 15
Then the mean
3+6+9+12+15
5
= 9
and the median (middle element is 9) are equal !"