Examining Differential Item Functioning in the Household Food Insecurity Scale: Does Participation in SNAP Affect Measurement Invariance?

The Household Food Security Survey Module (HFSSM) is a scale used by the U.S. Department of Agriculture to measure the severity of food insecurity experienced by U.S. households. In this study, measurement invariance of the HFSSM is examined across households based on participation in the Supplemental Nutrition Assistance Program (SNAP). Households with children who responded to the HFSSM in 2015 and 2016 (N = 3,931) are examined. The Rasch model is used to analyze differential item functioning (DIF) related to SNAP participation. Analyses suggest a small difference in reported food insecurity between SNAP and non-SNAP participants (27% versus 23% respectively). However, the size and direction of the DIF mitigates the impact on overall estimates of household food insecurity. Person-fit indices suggest that the household aberrant response rate is 6.6% and the number of misfitting households is comparable for SNAP (6.80%) and non-SNAP participants (6.30%). Implications for research and policy related to food insecurity are discussed.