That used to be a simple question to answer. I would have told you to find a document on CIC's website (http://www.cic.gc.ca/english/resources/manuals/ip/ip08-eng.pdf) and look at the flowchart on page (49?) to answer your question. Unfortunately (but not surprisingly) that flowchart has been removed.
You should still read through the new version of IP8, just for fun, or just start on page 20. Your question is eventually answered on page 22, section 5.15.
Good luck!
*edit* this wold be for an Inland applicant, but the eligibility requirements to apply for Outland sponsorship should be pretty close, except for the cohabiting with sponsor part.