Tyrone is interested in conducting a study to investigate what type of dog food dogs prefer. He selects two brands of canned dog food: Brand A, a chicken-based dog food; and Brand B, a beef-based dog food. In the morning, he feeds 20
dogs Brand A and records how much food is left after one hour. In the afternoon, he feeds 20 different dogs, of the same
age and type, Brand B. Again, he records how much food is left after one hour. He finds that cats eat significantly more of
Brand B than Brand A.
What type of design has Tyrone used in his study?