Average list from many lists in a [coll]

Hi there,
do anyone have idea how to make average list from many lists stored in [coll] ?

Lists will be added during patch's life, so number of lists is unknown and theoretically it will be lot of lists.
Number of numbers in list is only about 17.
I'm trying to process some interactive statistical data...
Jitter?

Many thanks for any input,
Serge