Research methods in nutrition and dietetics: design, data analysis, and presentation.

Most problems in practice may be addressed through research. To show the applicability of research to all areas of nutrition and dietetics, seven types of research designs are discussed in this article: qualitative research; case series and surveys--both categorized as descriptive research; and experimental design, quasiexperimental design, cohort (follow-up) studies, and case-control studies--the four of which are categorized as analytical research because each design tests hypotheses of causal relationships. Sample size, subject selection, and statistical analysis and interpretation are discussed as appropriate to each research design. Numerous examples are presented, along with the basic research designs. Each section and subsection is numbered so that the article can serve easily as a reference and its component parts can be accessed readily. Research provides answers to questions and, generally, raises further questions that future research can address. Among the benefits of well-designed research are answers to clearly stated research questions, useful comparisons between options, information to guide evaluations of protocols, and data to document and support one's professional activities and one's staff.