Morgan S Lee1, April Idalski Carcone2, Linda Ko3, Noel Kulik4, Deborah A Ellis5, Sylvie Naar6. 1. CommunicateHealth, Inc, Rockville, MD. 2. Division of Behavioral Sciences, Department of Family Medicine and Public Health Sciences, Wayne State University, Detroit, MI. Electronic address: acarcone@med.wayne.edu. 3. Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA. 4. Division of Kinesiology, Health and Sport Studies and the Center for Health and Community Impact, College of Education, Wayne State University, Detroit, MI. 5. Division of Behavioral Sciences, Department of Family Medicine and Public Health Sciences, Wayne State University, Detroit, MI. 6. Department of Behavioral Sciences and Social Medicine, Florida State University, Tallahassee, FL.
Abstract
OBJECTIVE: The goal of this study was to explore the impact of 5 decision rules for removing outliers from adolescent food frequency questionnaire (FFQ) data. DESIGN: This secondary analysis used baseline and 3-month data from a weight loss intervention clinical trial. PARTICIPANTS: African American adolescents (n = 181) were recruited from outpatient clinics and community health fairs. VARIABLES MEASURED: Data collected included self-reported FFQ and mediators of weight (food addiction, depressive symptoms, and relative reinforcing value of food), caregiver-reported executive functioning, and objectively measured weight status (percentage overweight). ANALYSIS: Descriptive statistics examined patterns in study variables at baseline and follow-up. Correlational analyses explored the relationships between FFQ data and key study variables at baseline and follow-up. RESULTS: Compared with not removing outliers, using decision rules reduced the number of cases and restricted the range of data. The magnitude of baseline FFQ-mediator relationships was attenuated under all decision rules but varied (increasing, decreasing, and reversing direction) at follow-up. Decision rule use increased the magnitude of change in FFQ estimated energy intake and significantly strengthened its relationship with weight change under 2 fixed range decision rules. CONCLUSIONS AND IMPLICATIONS: Results suggest careful evaluation of outliers and testing and reporting the effects of different outlier decision rules through sensitivity analyses.
OBJECTIVE: The goal of this study was to explore the impact of 5 decision rules for removing outliers from adolescent food frequency questionnaire (FFQ) data. DESIGN: This secondary analysis used baseline and 3-month data from a weight loss intervention clinical trial. PARTICIPANTS: African American adolescents (n = 181) were recruited from outpatient clinics and community health fairs. VARIABLES MEASURED: Data collected included self-reported FFQ and mediators of weight (food addiction, depressive symptoms, and relative reinforcing value of food), caregiver-reported executive functioning, and objectively measured weight status (percentage overweight). ANALYSIS: Descriptive statistics examined patterns in study variables at baseline and follow-up. Correlational analyses explored the relationships between FFQ data and key study variables at baseline and follow-up. RESULTS: Compared with not removing outliers, using decision rules reduced the number of cases and restricted the range of data. The magnitude of baseline FFQ-mediator relationships was attenuated under all decision rules but varied (increasing, decreasing, and reversing direction) at follow-up. Decision rule use increased the magnitude of change in FFQ estimated energy intake and significantly strengthened its relationship with weight change under 2 fixed range decision rules. CONCLUSIONS AND IMPLICATIONS: Results suggest careful evaluation of outliers and testing and reporting the effects of different outlier decision rules through sensitivity analyses.
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