In food-producing animal clinical studies, the experimental unit can be an individual animal, a pen, a tank, a raceway, or a herd; while in human clinical studies, the experimental unit is usually a patient. Oftentimes in food-producing animal studies, a treatment group is randomly assigned to a pen of animals, and the pen of animals as a whole is treated (for example, given the same medicated feed or water) and statistical inference is made on the pen instead of individual animal. In addition, if multiple sites are used and site is treated as a random factor, study design and analysis become more complex. This presentation provides similarities and differences in study designs and analyses between food-producing animal and human clinical studies with a focus on demonstrating methods and discussing issues for sample size determination in food-producing animal clinical studies.