For an appropriately randomized experiment, it's important to consider the similarity within the population and the ability to randomly assign dietary treatments.
Among the populations listed:
- Population #1 (dogs in California) is quite broad and includes many different breeds and variables, making it harder to control for all factors that might affect activity levels.
- Population #2 (golden retrievers in Omaha, Nebraska) is more specific, focusing on a single breed and location, which can help control for some variables but may limit generalizability.
- Population #3 (poodles in the United States), while also breed-specific, is quite broad geographically, which could introduce variability in diet and lifestyle based on different regions.
The most appropriate choice for conducting an experiment while ensuring randomization and control over breed-related factors seems to be Population #2: golden retrievers in Omaha, Nebraska. This allows for good control over the breed and can minimize confounding factors associated with different locations.