Suppose you are interested in the effects on boys of different dosages of a new drug to treat adhd. you set up an experiment to consider the factor of dosage with two levels (300 mg vs. 500 mg). which would be the best choice for the different treatment groups of the experiment within each block? a. three groups: no drug, 300 mg of new drug, 500 mg of new drug. b. two groups: placebo drug and either 300 mg of new drug or 500 mg of new drug. c. four groups: no drug, placebo drug, 300 mg of new drug, 500 mg of new drug. d. three groups: placebo drug, 300 mg of new drug, 500 mg of new drug. e. two groups: 300 mg of new drug and 500 mg of new drug.