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

D. Incomplete randomization

Step-by-step explanation:

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.