Dr. kiecolt-glaser is a health psychologist studying whether stress impairs the body's ability to heal. in the highly stressful week before final exams, one group of dental students are given an oral punch biopsy—a small sample of gum tissue is removed. the number of days for the oral wound to completely heal is recorded. another group of dental students receive an oral punch biopsy during summer vacation. once again, the number of days until the oral wound completely healed was recorded. the two groups' gum samples were compared. which research method was used?

experimental

Explanation:

Based on the information provided within the question it can be said that the  research method that was used was experimental research design. This is a research method which follows the scientific method, meaning that it has a hypothesis, a manipulated variable, as well as other variables that are measurable, while the whole is experiment is completely controlled. Which seems to be the case in this scenario since there are controlled groups as well as a manipulated variable such as the oral punch biopsy given to some of the groups.

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c. wright mills's sociological imagination suggest investigating to explain this increase?