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Title: A guide for authors and readers of the American Society for Nutrition Journals on the proper use of P values and strategies that promote transparency and improve research reproducibility

Author
item SORKIN, JOHN - University Of Maryland School Of Medicine
item MANARY, MARK - Washington University
item SMEETS, PAUL - Wageningen University
item MACFARLANE, AMANDA - Carleton University - Canada
item ASTRUP, ARNE - Novo Nordisk, Inc
item DUGGAN, CHRISTOPHER - Harvard School Of Public Health
item HOGANS, BETH - Johns Hopkins University
item ODLE, JACK - North Carolina State University
item DAVIS, TERESA - Children'S Nutrition Research Center (CNRC)
item TUCKER, KATHERINE - University Of Maryland

Submitted to: The American Journal of Clinical Nutrition
Publication Type: Review Article
Publication Acceptance Date: 6/10/2021
Publication Date: 7/13/2021
Citation: Sorkin, J.D., Manary, M., Smeets, P.A., MacFarlane, A.J., Astrup, A., Duggan, C.P., Hogans, B.B., Odle, J., Davis, T.A., Tucker, K.L. 2021. A guide for authors and readers of the American Society for Nutrition Journals on the proper use of P values and strategies that promote transparency and improve research reproducibility. American Journal of Clinical Nutrition. https://doi.org/10.1093/ajcn/nqab223.
DOI: https://doi.org/10.1093/ajcn/nqab223

Interpretive Summary: In scientific research, the probability values (P values), derived from the estimate of the effect size and a measure of the precision of the estimate of the effect, have been used for over 100 years. Because of its long history, there is vast information about the misuse of P values within the scientific and medical literature. The respective Editors-In-Chief for the American Society for Nutrition journals, The Journal of Nutrition, The American Journal of Clinical Nutrition, Advances in Nutrition, and Current Developments in Nutrition, published an editorial article discussing the proper use of the P value consistent with the scientific method, strategies to promote transparency and improve research reproducibility. The authors focused on two main questions regarding P values: 1) What place should P values have in reporting the results of studies? 2) How should the perceived difficulty in replicating the results reported in published studies be addressed?

Technical Abstract: Two questions regarding the scientific literature have become grist for public discussion: 1) what place should P values have in reporting the results of studies? 2) How should the perceived difficulty in replicating the results reported in published studies be addressed? We consider these questions to be 2 sides of the same coin; failing to address them can lead to an incomplete or incorrect message being sent to the reader. If P values (which are derived from the estimate of the effect size and a measure of the precision of the estimate of the effect) are used improperly, for example reporting only significant findings, or reporting P values without account for multiple comparisons, or failing to indicate the number of tests performed, the scientific record can be biased. Moreover, if there is a lack of transparency in the conduct of a study and reporting of study results, it will not be possible to repeat a study in a manner that allows inferences from the original study to be reproduced or to design and conduct a different experiment whose aim is to confirm the original study’s findings. The goal of this article is to discuss how P values can be used in a manner that is consistent with the scientific method, and to increase transparency and reproducibility in the conduct and analysis of nutrition research.