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This is the third article in a periodic five-part series on publishing nutrition research. These monographs are designed to assist in the interpretation of the Journal of the American Dietetic Association author guidelines and provide guidance in publishing and interpreting nutrition-related research articles. This installment focuses on the use of nonparametric statistical methods. The rationale for their use, their advantages and disadvantages, nonparametric alternatives to parametric tests, nonparametric statistical analysis, examples of their use, and helpful resources for further study are topics and issues addressed in this article.

Members of the Board of Editors recognize the importance of providing a resource for researchers to insure quality and accuracy of reporting in the Journal. This second monograph of a periodic series focuses on study sample selection, sample size, and common statistical procedures using parametric methods, and the presentation of statistical methods and results. Attention to sample selection and sample size is critical to avoid study bias. When outcome variables adhere to a normal distribution, then parametric procedures can be used for statistical inference. Documentation that clearly outlines the steps used in the research process will advance the science of evidence-based practice in nutrition and dietetics. Real examples from problem sets and published literature are provided, as well as reference to books and online resources.

To enhance the Journal's position as the premier source for peer-reviewed research in the science of food, nutrition, and dietetics, members of the Board of Editors recognize the importance of providing a resource for researchers to ensure quality and accuracy of reporting in the Journal. This first monograph of a periodic four-part series focuses on the study hypothesis, study design, and collaboration with a statistician. The basics of study design start with a clear hypothesis or research question and a definitive outcome measure. Throughout the development of a research project, the questions of what is to be discovered and why the research is being conducted need to be addressed. Decisions about parameters to measure and study design most appropriate to test a hypothesis create the foundation for future conclusions. Collaboration with a statistician can aid in the research development process. Documentation that coherently communicates the research process will advance the science of evidence-based practice in nutrition and dietetics. Real examples from published literature are provided, as well as references to books and online resources.

Objective: To assess dietary supplement use and its association with micronutrient intakes and adequacy among 2,195 US men and women aged 40 to 59 years from eight diverse population samples surveyed by the International Population Study on Macronutrients and Blood Pressure., Design: Four 24-hour dietary recalls were collected, including information on dietary supplements. The Nutrition Data System (NDS) was used for nutrient analyses. Supplements not in NDS were classified separately (non-NDS). Intake of non-NDS supplements was documented. Participants were classified as not supplement users and supplement users, subclassified-due to concerns about nutritional value-as users of NDS supplements only (mostly vitamins and minerals) and users of non-NDS supplements (eg, botanicals, animal products, and enzymes). To assess effects of supplement use on micronutrient intake and adequacy, mean intakes from supplements, foods, and foods plus supplements were compared with Dietary Reference Intakes., Participants: Two thousand one hundred ninety-five US participants; 1,136 used supplements., Statistical Analyses: Chi 2 tests, multivariate logistic regression, and means were used to assess differences in and factors related to supplement use and to determine dietary adequacy., Results: Supplement use was more common among women, older participants, more educated participants, and Asian Americans. Body mass index and current cigarette smoking were significantly and inversely associated with supplement use; past smoking and education were significantly and positively associated with supplement use. Intake from foods plus supplements was considerably higher than from foods alone for vitamins A, C, and E; niacin; folate; and iron., Conclusions: Supplement use is common among middle-aged Americans and sizably increases daily intakes of several micronutrients. These data underscore the importance of dietary supplement assessment.