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To test an herbal treatment for headaches, 100 volunteers who suffered from mild headaches were randomly divided into two groups. Each person was given a month's supply of tea bags. For one group, the tea contained the herb mixed with green tea, whereas for the other group, the bags contained only the green tea. Participants were not told which type of tea they had, and were asked to drink one cup of tea per day for a month.
At the end of the month, a researcher evaluated them to determine if the length and number of headaches had improved. The researcher did not know which of the subjects had the tea with the herbal ingredient added.
Which is true regarding this study?
ANSWER:
Only (A) and (B) are true.
The study is double-blind, because the subjects didn’t know which tea they got (which protects against the placebo effect), and the researcher also didn’t know (which helps guard against researcher bias). In addition, the "only green tea" group serves as the control group because they didn’t get any active herbal ingredient.