Which of the following does not have a ratio of 2:3:4? O {2 x, 3 x, 4 x}
O {6 m2,9 m2, 12 m2
O {8, 15, 24)

Which of the following is the major negative aspect of crossover designs for research studies? a. prohibitive cost b. residual effects c-subject drepout d. incomplete randomization e. large sample size required