(2004; 98 pages)
5.2 Selection of study sites and study units
Before selecting health facilities, drug outlets, households or individuals, a researcher needs to identify relevant study sites or in other words, the population from which a sample is to be drawn.
The selection of study sites depends both on the objectives of the study and on pragmatic factors (such as the distance to be travelled, the willingness of key individuals to be involved in future rational drug use interventions, and contacts which can facilitate entry into the community).
The research objectives provide the researcher with criteria to select study sites. For example, a study on treatment practices in childhood malaria is best done in communities with a high incidence of malaria.
The next step is to consider the heterogeneity of the potential study population
- i.e. households with children who live in malaria-endemic areas. If economic status or educational level are important factors, the researcher may want to select communities with different socio-economic profiles.
In the preparatory phase of a study, researchers should identify various research sites, taking into consideration the research objectives. During on-site visits, they should discuss the study’s objectives and plans for future research with health programme managers, community leaders and representatives of other relevant institutions. Final selection of study sites is based not only on the research site characteristics, but also on the willingness of health workers and community leaders to participate in and facilitate the study, and conduct the research.
When the research sites have been selected, the researchers need to decide on the sampling method to be used to select the study units: health facilities, drug outlets, individuals and/or households in the community. The most commonly used qualitative and quantitative sampling methods are discussed below.