To test an herbal treatment for depression, 100 volunteers who suffered from mild depression were randomly divided into two groups. Each person was given a month's supply of teabags. For one group, the tea contained the herb mixed with a spice tea, and for the other group, the bags contained only the spice tea.
Participants were not told which type of tea they had. They were asked to drink one cup of tea per day for a month. At the end of the month, a psychologist evaluated them to determine if their mood had improved. The psychologist did not know who had the tea with the herbal ingredient added.
a. Was this study an observational study or an experiment? Explain briefly.
b. Did this study have a placebo group? Explain briefly.
c. Was this study double-blind? Explain briefly.