At the scale of a McDonalds ad campaign that seems easy to measure: go to the nearest Target parking lot and ask as many people as you can two questions: "are you vegetarian" and "did you see {description of ad here}". Then compare how which percentage of vegetarians saw the ad compared to the percentage of non-vegetarians saw the ad. There are even companies specialized in market research that will do this in a more representative and statistically rigorous way

Doesn’t Google earn more from McDonalds if Google provides McDonalds with a higher click through rate? If you’re providing a high click through rate, you’ve probably done the due diligence to screen vegetarians already

Can't they ask claude to create account do some relevant searches and then check if ad is shown?