When conducting a scientific investigation, scientists try to remain objective and design experiments that avoid bias. Which of the
following is an example of a biased experimental design?
I. A new drug is being studied by a university. One group is given the drug, and the control group is not aware they are being
given a placebo (sugar pill).
II. A shampoo company has its own laboratory test its new product. The laboratory concludes that the shampoo is safe and
effective, so the company prints this on the bottle.
III. A medical student is researching the health benefits of yoga, so she picks fifty females around her age to participate in the
study.
IV. A farmer is comparing a new fertilizer to his old one. He uses the new fertilizer on an irrigated field, and his old fertilizer on a
field that only receives rainwater.
OA. I, II, III, and IV
OB. II and IV only
OC. I only
OD. II, III, and IV only