According to a recent warning from the FDA, grain-free food might be giving dogs a life-threatening heart problem called dilated cardiomyopathy, or DCM. A public relations firm representing a major brand of dog food was wondering if there had been a shift (from what was historically typical) in the percentage of dog food being bought from the following categories after the FDA released its warning: expensive grain-free dog food, cheap grain-free dog food, expensive dog food with grain included, and cheap dog food with grain included. Required:
What hypothesis test would be appropriate for analyzing the above scenario?