A group of 11 mice was given water, and another group of 10 mice was supplied with diluted black coffee (coffee:water 1:1) as drinking fluids for five weeks. The composition of the diets and living conditions were similar for both groups of mice. Blood glucose was monitored weekly for all mice. After five weeks, there was no change in average body weight between groups. Results indicated that blood glucose concentrations increased significantly in the mice that drank water compared with those that were supplied with coffee. Finally, blood glucose concentration in the coffee group exhibited a 30 percent decrease compared with that in the water group.

(In the original paper*, the investigators acknowledged that the coffee for the experiment was supplied as a gift from a corporation.)

Answer the following questions:

1. What was the hypothesis of this experiment? (Reminder: Hypothesis is a statement.) What question(s) was (were) the investigator asking?

2. Which is the control group? Why?

3. Which is the treatment group? Why?

4. Did the researchers follow the scientific method in their experimental design? Explain.

5. Do you think that there may be any possible biases or other problems in this experiment? Explain.

6. Based on the data, was the hypothesis supported, and what can you conclude from this experiment?