Answer:
A. We know that this was an experiment rather than an observational study because treatments were administered, with the first group receiving the experimental drug, the second group receiving a placebo, and the third group receiving no treatment."
B. The factors are the variables. The independent variable was group three that received no treatment, while the dependent variables were the first and second groups that received some treatments. Another variable is the change in blood pressure recorded at the end of the period.
The levels refer to the different treatments that were administered to the three groups: experimental drug, placebo, and no treatment.
C. The principles of experimental design are Randomization, Repetition, and Control. We are not aware of how the participants were chosen and this experiment was not replicated in the scenario. We can affirm that there is Control because the three groups were not given the same treatment.
Explanation:
In an observation, the researcher does not attempt to change any variables. She simply observes and then records her observations. In an experimental study, the researcher creates a control group and, also at least, one testable group. The purpose is to compare the control group and the testable group.