What is the average or common probability that NEW volunteer nodes will finish the assigned tasks?

For example: in
We know that in history of a baseball player, most batting averages over a season have hovered between something like .215 and .360, with some extremely rare exceptions on either side.

When new node join the pool, there is ratio that might assigned to this nodes that represent the likelihood that node will compete that task.

If there is, can I have resource.