What is a good win rate in Sit and Go's

[Roy Munson]

I am a long time cash game player who has recently become addicted to the online one table sit and go tournaments. I like to play one while playing a couple of other cash games.

What is a decent win percentage?
How often should one finish in the money? And what should the ratio of 1sts to 2nds and 3rds be?
How many does one need to play to have a significant meaningful sample size?

I have 150 in my Poker Tracker database but I doubt that I can draw any conclusions from that amount.

Thank you in advance.