A Scientist Is Designing a Clinical Trial to Test the Effect

Multiple Choice

A scientist is designing a clinical trial to test the effect of online chat counseling with migraine sufferers as a supplementary treatment in combating their migraines. Migraine sufferers will have access to counselors via online chat software; the scientist plans to see whether their migraine pain has been reduced after six weeks.
Preliminary information suggests that the effect of (face-to-face) counseling is larger for migraine sufferers who are women than men. Knowing this, the scientist would probably use a:

A) stratified random sample.
B) completely randomized design.
C) block design, with counseling and no counseling as the blocks.
D) block design, with women and men as the blocks.