Odds of a major downswing?

[PartySNGer]

I've tracked every $55 SNG since Party started allowing 10 tables, whether I was drunk, on tilt, whatever. Since then I've played 1540 $55s with a ROI of 14.5% (including a recent downswing). In October and November, my worst 300 SNG stretch was winning $1300. Over my last 299 SNGs I have lost $582.

OK, I've seen posts where Irieguy says even the best players will lose over 100-150 SNGs. I'm just wondering what the odds are that a long term 15% ROI player could lose 11 buy-ins over a 300 SNG stretch. I'm not even overly pissed, just wondering how big a statistical anomaly this is. I imagine there's less than a 1% of this occurring. Hopefully, Irie or someone will know more.