Disentangling mode-specific selection and measurement bias in social surveys
In 2011, Statistics Netherlands conducted a large-scale mixed-mode experiment linked to the Crime Victimization Survey. The experiment consisted of two waves; one wave with random assignment to one of the modes web, paper, telephone and face-to-face, and one follow-up wave to the full sample with interviewer modes only. The objective of the experiment is to estimate total mode effects and the corresponding mode effect components arising from undercoverage, nonresponse and measurement. The estimated mode effects are used to improve methodology for mixed-mode surveys. In this paper, we define mode-specific selection and measurement bias, and we introduce and discuss estimators for these bias terms based on the experimental design. Furthermore, we investigate whether mode effect estimators based on the first wave only, reproduce the estimates from the full experimental design. The proposed estimators are applied to a number of key survey variables from the Labour Force Survey and the Crime Victimization Survey.