The researchers chilled the beverages to 6°C. Participants drank the beverages at the same time each day for three days. During the 3 days of the experiment, the researchers feed each participant the same diet. On the third day participants spent 24 hours in a calorimeter chamber to measure their energy metabolism. The medical journal Obesity published the results in 2007. What is the purpose of double-blinding? a. To control unintentional researcher bias in the execution of the experiment
b. To control for the participants' prior beliefs about energy drinks
c. To control both unintentional research bias and participant prior beliefs