Conditioning on "study" is essential for valid inference when combining individual data from multiple randomized controlled trials: a comment on Reesor et al's School-based weight management program curbs summer weight gain among low-income Hispanic middle school students. J Sch Health. 2019;89(1):59-67.

Address: Department of Applied Health Science, School of Public Health, Indiana University, Bloomington, IN 47404.; Department of Applied Health Science, School of Public Health, Indiana University, Bloomington, IN 47405.; Department of Nutritional Sciences, Texas Tech University, Lubbock, TX 79409-2006.; Department of Human Development and Family Studies, Texas Tech University, Lubbock, TX 79409.; Division of Biostatistics and Department of Population Health, New York University School of Medicine, New York, NY 10016.; Department of Epidemiology and Biostatistics, School of Public Health, Indiana University, Bloomington, IN 47405.