title: Differential item functioning analysis of the 2003-04 NHANES physical activity questionnaire.
abstract: Using differential item functioning (DIF) analyses, this study examined whether there were any DF items in the National Health and Nutrition Examination Survey (NHANES) physical activity (PA) questionnaire. A subset of adult data from the 2003-04 NHANES study (n = 3,083) was used. PA items related to respondents' occupational, transportation, domestic, leisure-time, strength-related, and sedentary activities were analyzed for DIF using Mantel-Haenszel, SIBTEST, and analysis of variance procedures. Some items were identified as DF items, with the majority of those items favoring advantaged social groups. For example, items about domestic activity and moderate-intensity leisure-time activity were DF items favoring non-Hispanic Whites, and persons with higher levels of education (e.g., some college or more) or income (e.g, annual family income [AFI] > $34,999). The vigorous activity item was a DIF item favoring younger adults (ages 20-59 years) and persons with higher levels of education or income. Occupational PA presented DF favoring Hispanics and persons with lower levels of education (e.g., high school or less), and the transportation-related PA item presented DF favoring persons with lower incomes (e.g., AFI $34,999). These findings highlight the importance of conducting DF analysis in PA survey construction and emphasize the need to introduce DIF concepts and methods to PA researchers.
authors.affiliation: Department of Kinesiology, Boise State University, Boise, ID 83725, USA. yonggao@boisestate.edu
authors.forename: Yong
authors.initials: Y
authors.lastname: Gao
authors.forename: Weimo
authors.initials: W
authors.lastname: Zhu
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003627:Data Interpretation, Statistical; D004522:Educational Status; D005260:Female; D006306:Health Surveys; D006801:Humans; D007182:Income / Q000706:statistics & numerical data; D008297:Male; D009043:Motor Activity; D044469:Racial Groups / Q000706:statistics & numerical data; D014481:United States; D055815:Young Adult