Adults with more than a twelve (12)-month history of migraines were assigned randomly in a double-blinded study to receive treatment with experimental drug x (10 or 20 mg/day) or placebo. the primary efficacy measure was the reduction in severity of the migraine attacks. enrollment was twelve-hundred (1200) subjects. which of the following best describes the clinical phase of this study

Phase III.

Explanation:

Clinical research includes the different steps to test the particular drugs and its use for the medical treatment. Clinical research is divided into four main phases.

The phase III of the clinical research includes the double blinded study and its clinical trial on the patients. This phase determines the drug safety and efficacy. The therapeutic effect of the drug is tested directly in phase III of the clinical trial.

Thus, the answer is phase III.

it will increase due to the time span