A Psychiatrist Tells You That She Is Interested in Determining

A psychiatrist tells you that she is interested in determining if the condition of individuals who are clinically depressed improves with either 20 or 40 milligrams of Prozac.She decides to administer 20 milligrams to a random half of her clients,and 40 milligrams to the other half.She finds that after 6 months,the clients who took 40 milligrams of Prozac are significantly less depressed than those clients who took 20 milligrams of Prozac.Which type of study did the psychiatrist conduct?

A) correlational research
B) experimental research
C) controlled research
D) hypothetical research