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Placebo and Double-blind Technique

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Explain the importance of the Placebo, and the double-blind technique in carrying out research studies.

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Explains the importance of the Placebo, and the double-blind technique in carrying out research studies.

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1. Explain the importance of the Placebo, and the double-blind technique in carrying out research studies.

Let's look at a brief overview of the experimental design first; in other words, the bigger picture. It will help to understand the terms of placebo and the double-blind technique and the importance in carrying out research studies.


The purpose of experimental method is to determine causes of behavior (e.g. what causes

For example, an experiment is designed to test a hypothesis (a prediction about a cause-effect relationship between two or more variables) such as poor nutrition causes increased the rate of depression in women. The variable of nutrition would be the variable that we vary (poor nutrition versus good nutrition) to see if it has an effect (i.e., causes) the rate of depression in the women (i.e., women that we randomly select and assign to two groups).

In our example, the researcher needs to control of both the independent variable and the extraneous variables that can affect the outcome of the experiment. In this example, the researcher controls for the various levels of the independent variable (IV), the levels of nutrition. In other words, in the poor nutrition group (one level of the IV) the researcher controls the nutritional level of the participants. Likewise for the level two of the IV (high nutrition group), the research also has control over the nutritional level. This control over the IV levels could be done by: 1) assigning a specific diet for the participants to follow or 2) through assignment of self-reported poor nutrition participants to one group and the high nutrition participants to another group and finally, random assignment of the participants for the control group).

The researcher has control over the control group through random assignment to the control group. In other words, this control group that is similar to the experimental group and is exposed to the same experiential environment but is NOT exposed to the independent variable; the group is used for comparison. Thus, in our example nutrition would not be controlled for (i.e., eat whatever).

At the end of the experiment, the three groups would be compared on the measure of the depression (referred to the DV --measured through a depression test, for example). If we found a significant difference, then we could rule out the experimental conditions as having caused the experimental effect (i.e., increase in depression—the ...

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