A study included 60 people who experience ordinary headaches. Of the participants, 20 received aspirin, 20 received a placebo, and 20 received nothing at all. In 65 percent of the aspirin group, the headache disappeared. In the other two groups, the "cure" rates were 35 and 5 percent, respectively. Other than the drug condition, the participants were treated identically. This study:

Question

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This study is an experimental study because it involves the manipulation of an independent variable (the treatment condition: aspirin, placebo, or nothing) to observe its effect on a dependent variable (whether the headache disappeared). The presence of a control group (those who received nothing) and a placebo group helps to isolate the effect of the aspirin.

A Study Included 60 People Who Experience Ordinary Headaches