Research Topic and Sampling
So far, we have spoken of samples of people. The subject of research may, however, relate to any objects, for example, organizations, health systems, or health promotion programs. The research question and the study design determine the subjects of the sample and how they are selected. Take as an example the Waxman Report we introduced in Week 2. The study was commissioned by a policy maker in order to evaluate the scientific accuracy of the content of these educational programs. The sample in this study is not people but 13 of the most popular abstinence-only curricula.
Biomedical researchers focus on how the body works. They consider the biological processes, structures, functions and mechanisms within an organism. Biological and clinical researchers focus their attention on the individual. They study the response of the body to various preventative, diagnostic, or therapeutic interventions. Public health researchers study groups of people (populations). They conduct epidemiological research, which considers the frequency, distribution, and causes of ill health. Such research studies could be retrospective, studying events that already happened or prospective, studying events as they happen.
Research into health systems and health administration deals with the functioning of the health system, the costs and quality of the services provided, and the distribution of resources within the system. Samples in such research may be drawn from organizations, programs, or geographical units. A study may examine the profitability of nursing homes in rural areas. Another may assess the cost-effectiveness of preventive measures among the urban poor.
Sampling and Research Conclusion
The incidence of obesity has reached epidemic proportions in the U.S. One of the causes of obesity is physical inactivity. Technological advances make much household work and other labor unnecessary. Physical activity would now come mainly from sport and other recreational activities. Are there sufficient opportunities for recreational activities? If there are, can we expect that people use them? Further, can we expect a reduction in the incidence of obesity?
Google and briefly read about the HOP’N After-School Project (Dzewaltowski et al., 2010), which looks into the relationship between recreation and obesity. Recreation supply is the independent variable and healthcare expenditure is the dependent variable in this study. Recreation supply, by increasing physical activity, is expected to have an effect on health status and obesity. An interesting point here is that improved health may lead to greater physical activity. The causal relationship may run both ways.
The sample in the Dzewaltowski et al. study consisted of 961 children at 8 sites. The study was originally powered to detect a .5 kg/m2 difference in BMI between a sample size of 4 intervention and 4 control schools with a reduction in the detectable difference adjusting for age, ethnicity, and gender using 20 students per group. The study explains that in each sample, there is a control site and an intervention site, with data revealed that compares the sites in the tables.
Note the care taken in selecting the sample and the level of detail. This can be the standard for rigorous sampling. Keep it in mind when you evaluate research with the focus on sampling in this week’s assignments.
Dzewaltowski, D. A., Rosenkranz, R. R., Geller, K. S., Coleman, K. J., Welk, G. J., Hastmann, T. J., & Milliken, G. A. (2010, December 13). HOP’N after-school project: An obesity prevention randomized controlled trial. International Journal of Behavioral Nutrition and Physical Activity, 7, 90-101