A statistician designs an experiment that tests the effectiveness of a drug. Which process can invalidate the results of the experiment? A. assigning subjects a unique identification number

B. assigning subjects into groups using a randomized process

C. selecting subjects in favor of the treatment

D. selecting subjects randomly for a control group

I think the answer is D not too sure tho

The question is kind of confusing. if it's asking how many variations of answers can you give. then do 4^5 for your answer.this would be something like the first question could be a and the 2nd c or first b next c etc. if you can, ask the teacher for a better confirmation of what it's asking. if i'm assuming correctly what it's asking, it's 625 different variations.