Final answer:
A scientist using two genetically identical lab rats, with one receiving a placebo and the other the actual medicine, is conducting a controlled experiment. This research method allows for the effects of the medicine to be compared against the placebo, employing a control group to reduce bias, often via a double-blind setup. The answer is A. a controlled experiment.
Step-by-step explanation:
The scientist testing the effectiveness of a new medicine by using two genetically identical lab rats, with one receiving a placebo and the other the actual medicine, is conducting a controlled experiment. This is a form of experimental research where one group receives the treatment (in this case, the actual medicine) and the other receives a placebo to serve as the control group. The aim is to measure and compare the effects of the treatment on both groups to see if the medication has any significant effect. Controlled experiments are essential in scientific research to limit the effects of variables other than the one being tested, and they are often double-blind to reduce bias, meaning that neither the participants nor the researchers know who is receiving the actual treatment or the placebo.
In contrast, an observational study involves observing subjects in their natural environment without any intervention by the researcher. Surveys typically consist of questionnaires answered by participants and are another non-experimental research method. In this scenario, the method being utilized is a controlled experiment as there is a deliberate manipulation of the independent variable (the medicine) and the presence of a control group receiving a placebo.
The correct answer for the method being used to investigate the effectiveness of the medicine is: A. a controlled experiment.