When conducting an experiment for a new heart burn medicine, researchers randomly assigned patients to take either the new drug, an existing heart burn medication, or a placebo. All medications looked the same, and patients were not told which one they received.

Was this experiment blinded?

• No, because the rearchers knew who got which medication
• No, because it was double blinded
• Yes, because a control group was used
• Yes, because the patients don't know which medication they received