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Figure 4.4 illustrates a typology of basic research designs. The first major distinction is between observational and experimental designs.

ssss1 Basic research design options in medical anthropology and neighboring disciplines.

Experimental Designs Experimental designs are distinguished by two features: random allocation and manipulation of the key causal variables. In classic experiments, researchers randomly assign participants to either an intervention or control group and measure one or more dependent (outcome) variables in both groups. Participants in the intervention group are then exposed to a treatment designed to test the causal effect of an independent (explanatory) variable, and both groups are measured again on the dependent variable. Random allocation, when done well, makes groups comparable with respect to unmeasured variables, such that whatever differences emerge between groups after the intervention are likely to reflect the true causal effect of the intervention.

Experimental designs are not common in medical anthropology, but there are successful examples. Shain et al. (1999) combined ethnography and a randomized trial to test the effect of culture- and gender-specific interventions to prevent sexually transmitted infections in African-American and Mexican-American women in San Antonio, TX. They first collected ethnographic data (observations, 25 focus-group discussions, 102 in-depth interviews) on the cultural context of sexual behavior, perceptions of risk, and motivations for behavior change. They used this information to design culturally appropriate messages about recognizing risk, committing to change, and communicating about sex. Then, 424 Mexican-American and 193 African-American women were randomly assigned to receive either the culturally appropriate messages (intervention group) or standard counseling (control group). One year later, Shain et al. found that women in the intervention group were 49% less likely to have a sexually transmitted infection than were the controls.