Dr. L. is planning a large-scale learning experiment. He would like to have 100 rats in one treatment group and another 100 in the other group. Because he needs so many rats, he says, "Well, I can't test all these animals by myself. I'll ask Dr. P. to help me. He can run the animals in the one group while I test the animals in the other group."

a. Knowing what you know about con- founding, is Dr. L.'s solution a good one? What can happen if one experi- menter tests all the subjects in one group while another tests all the subjects in another group?

b. Given what you know about balancing procedures, work out a better plan for Dr. L.