Contents

CHAPTER 6: Independent Groups Designs 201Key Concepttaken by the experimental participants, and not the participants’ expectationsabout receiving a drug.The use of placebo control groups in combination with a double-blind procedurecan control for both demand characteristics and experimenter effects.In a double-blind procedure, both the participant and the observer are blindto (unaware of) what treatment is being administered. In an experiment testingthe effectiveness of a drug treatment, two researchers would be needed toaccomplish the double-blind procedure. The first researcher would preparethe drug capsules and code each capsule in some way; the second researcherwould distribute the drugs to the participants, recording the code for eachdrug as it was given to an individual. This procedure ensures there is a recordof which drug each person received, but neither the participant nor theexperimenter who actually administers the drugs (and observes their effects)knows which treatment the participant received. Thus, experimenter expectanciesabout the effects of the treatment are controlled because the researcherwho makes the observations is unaware of who received the treatment andwho received the placebo. Similarly, demand characteristics are controlledbecause participants remain unaware of whether they received the drug orplacebo.Experiments that involve placebo control groups are a valuable researchtool for assessing the effectiveness of a treatment while controlling for demandcharacteristics. The use of placebo control groups, however, does raise specialethical concerns. The benefits of the knowledge gained using placebo controlgroups must be evaluated in light of the risks involved when research participantswho expect to receive a drug may instead receive a placebo. Typically, theethics of this procedure are addressed in the informed consent procedure priorto the start of the experiment. Participants are told they may receive a drug ora placebo. Only individuals who consent to receiving either the placebo or thedrug participate in the research. Should the experimental drug prove effective,then the researchers are ethically required to offer the treatment to participantsin the placebo condition.ANALYSIS AND INTERPRETATION OF EXPERIMENTAL FINDINGSThe Role of Data Analysis in Experiments• Data analysis and statistics play a critical role in researchers’ ability to makethe claim that an independent variable has had an effect on behavior.• The best way to determine whether the findings of an experiment arereliable is to do a replication of the experiment.A good experiment, as is true of all good research, begins with a good researchquestion. We have described how researchers use control techniques todesign and implement an experiment that will allow them to gather interpretableevidence to answer their research question. However, simply conductinga good experiment is not sufficient. Researchers must also present the evidencein a convincing way to demonstrate that their findings support their conclusions