The use of classic nonparametric tests (cNPTs), such as the Kruskal-Wallis and Mann-Whitney U tests, in the presence of unequal variance for between-group comparisons of means and medians may lead to marked increases in the rate of falsely rejecting null hypotheses and decreases in statistical power. Yet, this practice remains prevalent in the scientific literature, including nutrition and obesity literature. Some nutrition and obesity studies use a cNPT in the presence of unequal variance (i.e., heteroscedasticity), sometimes because of the mistaken rationale that the test corrects for heteroscedasticity. Herein, we discuss misconceptions of using cNPTs in the presence of heteroscedasticity. We then discuss assumptions, purposes, and limitations of 3 common tests used to test for mean differences between multiple groups, including 2 parametric tests: Fisher's ANOVA and Welch's ANOVA; and 1 cNPT: the Kruskal-Wallis test. To document the impact of heteroscedasticity on the validity of these tests under conditions similar to those used in nutrition and obesity research, we conducted simple simulations and assessed type I error rates (i.e., false positives, defined as incorrectly rejecting the null hypothesis). We demonstrate that type I error rates for Fisher's ANOVA, which does not account for heteroscedasticity, and Kruskal-Wallis, which tests for differences in distributions rather than means, deviated from the expected significance level. Greater deviation from the expected type I error rate was observed as the heterogeneity increased, especially in the presence of an imbalanced sample size. We provide brief tutorial guidance for authors, editors, and reviewers to identify appropriate statistical tests when test assumptions are violated, with a particular focus on cNPTs.
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http://dx.doi.org/10.1093/ajcn/nqaa357 | DOI Listing |
J Intern Med
January 2025
Department of Medicine (Huddinge), Karolinska Institutet, Stockholm, Sweden.
Nutrients
January 2025
National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention, 27 Nanwei Road, Xicheng District, Beijing 100050, China.
Purpose: The aims of this study were to explore the differences in total body water and hydration status among Chinese children aged 6-17 years.
Methods: A cross-sectional study was implemented among children aged 6-17 years in China. The total body water (TBW), intracellular water (ICW), and extracellular water (ECW) were determined by bioelectrical impedance analysis (BIA).
Nutrients
January 2025
Department for the Promotion of Human Science and Quality of Life, San Raffaele Open University, Via di Val Cannuta, 247, 00166 Rome, Italy.
Background: Gender differences in metabolic response to lifestyle interventions remain poorly explored. This study aimed to evaluate the impact of a six-month Mediterranean diet (MD) intervention combined with regular physical activity on metabolic parameters in overweight adults.
Methods: A prospective cohort study was conducted in an obesity clinic in Rome, Italy, involving overweight adults (BMI ≥ 25 kg/m) motivated to improve their lifestyle.
Nutrients
January 2025
Department of Nutrition, General Hospital of Thessaloniki "G. Gennimatas", 41 Ethnikis Aminis Str., GR-54635 Thessaloniki, Greece.
Background/objectives: Feeding and eating disorders (FEDs) constitute an important mental health problem today, especially among youngsters. The Sick, Control, One, Fat, Food (SCOFF) questionnaire was developed 25 years ago and remains the most frequently applied screening tool for FEDs among adults and youngsters. The aim of the present study was to translate and adapt the SCOFF questionnaire to the Greek language, using a tertiary-setting adolescent sample.
View Article and Find Full Text PDFNutrients
January 2025
Department of Epidemiology and Biostatistics, School of Public Health, Xi'an Jiaotong University Health Science Center, No. 76, Yanta West Road, Xi'an 710061, China.
As a widely consumed, nutritious, and affordable food, eggs and their derivatives' impacts on obesity remain inconclusive. In this study, we aimed to determine the association between egg and egg-derived cholesterol consumption, and their change trajectories, with obesity among Chinese adults. : Longitudinal data collected by the China Health and Nutrition Survey from 1997 to 2015 were analyzed.
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