He decides to do an experiment to test what type of food will make his chickens fatter . before the experiment, the chickens weigh an average of 5 pounds . david makes two groups of chickens . he feeds group a rice everyday, and feeds group b corn everyday. after one month, david weighs the chickens to see if they gained any weight . group a weighs an average of 5 pounds and group b weighs an average of 7 pounds.