Can radial tires affect gas mileage?

Vindalou

I was out last week and realized my 2012 T@B's tires were badly worn.  I was able to get 2 new tires, but radials instead of bias.  However, after getting the new tires, I now get about 10-15%  worse gas mileage.  Anyone know if this is normal or is it possible that in replacing the tires the Schwab tire guys may have messed something up?

RZRBUG

I just completed an eight hundred mile trip on new radials.  There was a minute decrease in gas mileage, but I attributed it to a lot of steep, curvy roads in the Ouachita and Ozark Mountains.