the affect [- or is that effect?] of one noisy group

We are currently gathering more data on factors which affect our learning.
In our splendid class we have table groups. One particular group is quite often noisy and disruptive. They claim that they are on task, which often they are. What I am interested in finding out is how does it affect the rest of you? Can you explain in polite terms how it affects the working environment in the class? Maybe it has a positive influence by adding amusement or perhaps it could be like the music and somehow create positive working energy. Maybe you find it wastes time and creates negativity. Possibly it could be a balance of the two and it may depend on picking the right time to chat and share a laugh.
Feel free to add your hypotheses [- the plural of hypothesis, KarateKid].
:-)
Also please explain what hypothesis means.
And if you don't know, add it to your word study list.

N.B. I really enjoy the vibrancy of the people involved. I am simply concerned about the disruptiveness.

p.s. Can anyone tell me what N.B. stands for and what it means?