I recently bought a Powell Endurance 775. I took it out for the first time yesterday and was throwing a 1/2 oz. footbal jig. I was flipping it and casting it around, then  I went to set the hook on a bass and the rod snapped about 1/3rd down from the tip. My question is; could casting a flipping rod cause it to break, or was it most likely a defect in the rod? Thanks for the help.

Defect. Probably a small nick in the blank during transit.

You didn't hurt it by casting, that's a warranty claim right there!

That is what will normally happen with a factory defect or damage in shipping, you should send it back.  To me, if a rod doesn't break after the first couple of fish or the first couple of outings, it shouldn't be a warranty claim.  A defect will show itself pretty quickly.

No, casting a "flipping stick" is fine. Unless it was a "high Stick" hook-set, sounds like a manufacturing/shipping defect or damage.