Understanding, Confidence and Usefulness of Effect Size and Certainty of Evidence: A Cross-Sectional Survey Among Australian Dietitians

Purpose: Interpreting treatment effect size is essential for evidence-informed dietetic care, yet understanding of this competency among dietitians remains unestablished. Methods: We conducted a web-based cross-sectional survey of Australian dietitians (October 2024-February 2025). The survey assessed their understanding of effect size, presented using three absolute estimates (risk difference [RD], risk in treatment vs risk in control groups, number needed to treat [NNT]) and two relative estimates (relative risk [RR], odds ratio [OR]). We also assessed their confidence in determining correct effect size, their perceived usefulness of effect estimates and corresponding certainty of evidence. Results: Approximately 7697 dietitians received the survey link. 27 participated and 13 completers were analyzed. Correct understanding was higher for absolute than relative estimates (30.0% vs 18.2%). Risk in treatment vs risk in control groups was understood the most (41.7%) and RD, RR and OR the least (18.2% each). Confidence was highest for RR [mean (SD): 4.18 (1.25)] and lowest for NNT [3.40 (1.17)]. Perceived usefulness was highest for OR [4.69 (1.18)] and lowest for NNT [3.75 (1.76)]. Certainty of evidence was rated useful [5.69 (1.03)]. Conclusion: Based on a small sample, preliminary evidence suggests limited understanding of effect size among Australian dietitians, highlighting the need for further training and assessment in larger sample.