What is the difference between narrative non-fiction and Memoir?

OMG I was going to post the exact question, because to me they sound very similar.

Found this:
http://www.guidetoliteraryagents.com/blog/Talking+Memoir+And+Narrative+Nonfiction.aspx

Yes, great link. These terms get confusing. I'm often asked the difference between autobiography, memoir and lifestory writing. As far as I've been able to determine it goes like this:

Autobiography is generally chronological, covers the full lifespan to date, and is geared more toward documentation than interpretation.

Memoir is focused on a theme, generally covers a limited time period, relies heavily on interpretation of the events, and chronicles personal development and change.

Lifestory writing is freestyle, generally a pile of unrelated vignettes, informal in style.

Given that, I'm currently taking a continuing ed course in short story writing that's taught by a professor at Carnegie Mellon U. The theme of the class seems to be building tension in our work. Our most recent assignment is to write the beginning of an "imaginary" (fiction written as) autobiography. As far as I know, she is unaware I teach lifestory writing, so I think carefully how to phrase my question. "You want us to focus on some specific event and how the character reacts and develops as a result?" Yes. That's what she intends. Phew. I did not want to get into a battle over the semantics of genre labels.