A doctor wants to determine if a new medication for cholesterol is more effective than the previous medication. The doctor asks her patients if they would like to take part in a study for a new medication, and 30 patients currently taking medication for cholesterol volunteer to participate. Which of the following would be an appropriate procedure for this experiment?

(A)The doctor needs to randomly assign 15 patients to the new medication and 15 to the original medication to even out the variability between the patients.

(B)The doctor needs to assign the first 15 patients to the new medication and 15 to the original medication to even out the variability between patients.

(C)The doctor needs to let the 30 patients choose which medication they are going to take through use of a survey to determine whether they want to participate in the experiment.

(D)The doctor needs to randomly assign the 30 patients to the new medication to even out the variability between the patients and to determine if their cholesterol level is lowered.