A confidence-interval calculation gives a probabilistic estimate of how well a metric obtained from a study explains the behavior of your whole user population.
UX staff can be organized in two ways: centralized or decentralized (or a hybrid). The teams can also report into different parts of the bigger organization. There is currently no single best practice for these team-structure questions.
Tooltips are small user-triggered popups that explain UI elements when the user points to something. They are useful, but don't use them for critical information.
