My First Question - CC Plates for Stock Suspension?

So its a few days after I bought my 03 Mach 1 and have come up with my first question. The tires on the Mach are the OEM tires and they need replaced. The rear tires have very uneven wear. The outside of the tires have much more wear than the middle/inside of the tires. The front tires are fine, its just the rear. So whats the deal here? I have done a little research and have found info on CC plates, but they seem to be needed only when lowering or dealing with aftermarket suspensions. Any advice much appreciated.

I'm sure its not lowered. I should of thought of the alignment, it does wander around a little bit on the road. I'll have it done when I get new tires. The one thing that bothers me though is that both rear tires have exactly the same wear pattern. The outside tread column is much more worn than the rest, on both tires. I would think that if it hit a curb or something it would be just one tire. Anyways thanks for the help.