Tomato hornworms are infesting Jaime's tomato garden. He designs an investigation to determine if a pesticide or ladybug beetles will control the infestation better. Jaime used six tomato plants. He put hornworm insecticide

on three plants, and then released ladybugs into the garden. He observed that the plants with the insecticide

had fewer Hornworms than the plants with only ladybug beetles. The second year, Jaime used only insecticide

to control Tomato Hornworms, but the treatment was not as effective. How did the design of the investigation

make the results different for the second growing year?