Treating acne. An article in a medical journal reports an experiment to see if pulsed dye laser therapy is effective in treating acne. The article describes the experiment as a “randomized, controlled, single-blinded split-face clinical trial of a volunteer sample of 40 patients aged 13 years or older with facial acne conducted at an academic referral center from August 2002 to September 2003.” A split-face clinical trial is one in which one side of the face is treated and one side is not. What do you think “single-blinded” means here? Why isn’t a double-blind experiment possible?

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