inefficiency: many scientists - one research task?

[minimen]

If many scientists assigned on one research task is there an inefficiency?
What does poor, average, excellent mean?
I'm playing X-piratez mod, here we call 'em brainiers.

[Meridian]

If many scientists assigned on one research task is there an inefficiency?

yes

What does poor, average, excellent mean?

it doesn't mean much, better not to think about it
gruesome details are somewhere on ufopedia.org (and also here on the forum, but I'm lazy to search)

[DataTraveler]

on ufopaedia.org, select the XCOM: Enemy Unknown game on the left, then select Research, scroll down to Technical Details 👍🏻