Graduate assistantships at Stanford

Hi all,
I was hoping someone could answer a few questions I had regarding assistantship oppurtunities at Stanford.

  1. How competitive is it for a MS student to get appointed as a Research/Teaching Assistant?
  2. Is there a statistic available on what proportion of Masters students hold some sort of funded assistantship?
  3. What qualifications are vital to get appointed for these positions?
    Would really appreciate any help!