The studies are designed this way b/c it removes the power of suggestion and the double-blind study keeps both researchers and participants in the dark. So this compared to who is receiving the treatment which is relevant b/c it stops the researchers from accidentally overbalancing the study participants, or unintentionally favoring their assessment of the conclusions.
Good Afternoon,
I believe what you are speaking of may be the following. There is the equator is the center of the earth. Then, their is, on top of the equator, The Tropic of Cancer which passes through Cuba. On the bottom of the Equator, is the Tropic of Capricorn which passes through the Amazon Forest in South America. I hope that i have helped and good luck!
Thank you,
Darian D.